Fluid handling – Pressure modulating relays or followers – With counter-balancing pressure feedback to the modulating...
Patent
1980-09-15
1983-01-25
Cohan, Alan
Fluid handling
Pressure modulating relays or followers
With counter-balancing pressure feedback to the modulating...
13762415, G05D 1600
Patent
active
043698042
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an electrohydraulic translation apparatus comprising an electrically controlled valve body associated with an electronic control generator permitting a pressure to be obtained which is proportional to an electrical control magnitude. Such an apparatus can be utilized, in particular, for monitoring a hydraulic pressure in the control circuit of an automatic transmission, in particular, in a hydraulically controlled automatic gearbox for industrial vehicles.
In automatic gearboxes of this type, the hydraulic control system usually comprises one or more regulating valves intended to regulate one or more pressures to an optimum level corresponding to a predetermined operating mode. These regulating valves are most often controlled by an auxiliary pressure, termed the control pressure. This auxiliary pressure should be proportional to an electrical magnitude representative of the operating conditions of the vehicle, such as, for example, the rotational speed of the turbine of the hydrokinetic converter comprised by the gearbox, the vehicle speed, the engine load, etc. It is thus necessary to cause the control pressure supplied to the regulating valve to vary with precision, so as to follow perfectly the course of the electrical control signal.
Various electrohydraulic apparatuses have already been proposed for obtaining a pressure proportional to such an electrical control signal. To obtain satisfactory performance, it is necessary to utilize complicated and expensive structures. Such apparatuses, known as servo-valves, are utilized in high-cost servo-mechanisms in aeronautics, astronautics, robots, etc. Apparatuses of this type utilized in the present industrial field should be more economical and hence of simplified construction. Because of this, the conventional apparatuses are not in general capable of causing the hydraulic pressure to vary with the desired precision and reproducibility as a function of the variations of the electrical signal.
Certain conventional apparatuses utilize, for example, an electromagnetic attractive force acting on a movable part. These apparatuses, however, have little precision; their operation causes a delay to occur in the response to a control signal. This hysteresis, probably arising both from the magnetic circuit utilized and from the hydraulic system, alters the precision of pressure regulation. Apparatuses of this type are complex in practice, and thus costly, which limits the possibility of adapting them to automatic gear-boxes. Moreover, they are frequently sensitive to external stresses, and in particular to vibrations.
The object of the present invention is a particularly economical electrohydraulic translating apparatus, enabling a pressure to be varied proportionally to an electrical control signal, and which is easy to construct and very simple, and also which exhibits no hysteresis and has a low sensitivity to vibrations, thus ensuring excellent reproducibility of the results.
The electrohydraulic translating apparatus according to the invention and enabling a pressure to be obtained proportional to a control signal comprises a movable part subjected to a magnetic attractive force. According to the invention, the apparatus furthermore comprises means to cause the magnetic attractive force to vary periodically as a function of the control signal, such as to subject the movable part to a vibratory movement.
The apparatus preferably comprises an electronic servo-control current generator providing pulsed electrical signals of which the average value is under the control of the above-mentioned control signal.
In a preferred embodiment of the invention, the apparatus comprises an electromagnet coil mounted within a body of magnetic material having a fixed core provided with a central passage for the hydraulic fluid and a ball which can be displaced to block the said passage. The aforesaid ball, made of a non-magnetic material, is maintained in a mounting of a plate of magnetic material subjected to the attractive force of the electroma
REFERENCES:
patent: 3099995 (1903-08-01), Raufenbarth
patent: 3476128 (1969-11-01), Barker
patent: 3529620 (1970-09-01), Leiber
patent: 3621862 (1971-11-01), Wojtecki
Bouvet Jean M.
Quemerais Philippe
Cohan Alan
Regie Nationale des Usines Renault
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