FR2668557A1 - PROCESS FOR THE CONTROL OF AN ELECTROPNEUMATIC, OR ACTUATOR, ACTUATOR, OR CYLINDER. - Google Patents

Abstract

A known method, applicable in particular to the clutch of motor vehicles, for controlling an electro-pneumatic cylinder whose working chamber can, by means of two solenoid valves, be placed in communication with either a vacuum source or a pressure source has for disadvantage that rapid movements require large valve sections with which slow movements are not achievable in a sufficiently finely sensitive manner due to opening times that are too short. This is why, according to the invention, in the case where slow movement of the cylinder is required, the two solenoid valves are controlled with the same frequency but a variable pulse rate for each valve, thus allowing for minimal gas consumption under pressure to adjust the operating speed practically at will.

Description

Method for controlling an operating member, or

  rin, electropneumatic The present invention relates to a process for the

  control of an operating member, or jack, electropneuma-

  tick, the working chamber of which can be communicated by means of two electromagnetic valves, or

  with a vacuum source, or with a pressure source.

  A process of this kind is known, in connection with a corresponding actuator, or jack, thanks to DE-OS 3128486, process in which:

  a) the lifting height of the operating member is pre-

  in each position of its piston rod, b) the value of the maximum lifting height is each time stored in memory, and

  c) during each subsequent lifting process, the speed

  se of the lifting movement is changed from a high

  lifting device which is at a determined distance from the maximum position noted during the previous lifting process, so that the actuation of the operating member, or

  cylinder, can each time be adapted to specific requirements

  lières and, in particular in the case of the activation

  of a clutch, can first close it as fast-

  ment as possible and, from a preset position,

  activate it with a reduced operating speed.

  The speed of the lifting movement is varied (operating speed) by varying the quantities of pressurized gas flowing per unit of time into or out of the working space of the

  actuator, or actuator Such actuators, or

  rins, are preferably brought to operate in one of the working directions with a pressure lower or higher than atmospheric, while the movement in the other

  sense of work is achieved by establishing a community

  communication with the atmosphere; however, communication can also be established with a source of

  pneumatic pressure at another pressure level The diff-

  reference between the maximum position, noted each time during the previous lifting process, of the piston rod

  of the operating member, or jack, and the lifting position

  ge from which the maneuvering speed is caused to vary is predetermined and can be adapted in particular according to needs When it comes to actuating a clutch by the maneuvering member, or jack, this

  difference is determined for example by the value of the tra-

  jet between the first contact between the friction surfaces

  clutch and the end position of these surfaces

these.

  For these operating devices, or jacks, electric

  tromagnetic, the pressure gas is controlled with an open valve either to the vacuum source or

  towards the pressure source, the other valve remaining closed.

  This arrangement makes it possible to obtain an evacuation or filling

  quick wise of the working chamber as far as the

  connecting pipes, including valves, have di-

  sufficiently important mentions Because one of the

  valves is always closed air consumption is low

  ble However, a slow movement can only be obtained thanks to extremely short opening times, so that for example in the above-mentioned DE-OS it is proposed that

  one of the valves is actuated by rhythmic pulses

  mées, with a varied ratio of opening time to time

closing.

  It appears from the description that in this agency-

  the other valve is still closed.

  In a device according to GB-PS 1486822 the working chamber communicates, by means of a permanently open throttle, with the pressure source and, by

  through a solenoid valve, with the vacuum pump.

  In the case of this device a working pressure deter-

  mined can only be obtained through consumption

  because of the flow through the throttle

  constantly air which must again be evacuated by the

  valve intermediate Depending on the ratio between the

  throttling effects of the throttle valve and the po

  pressure tential available between the vacuum source and the pressure source is reduced in its action inside the working chamber Slow movement

  seems to be possible for sufficient opening times.

long.

  DE-PS 2927175 describes a device for

  automatic actuation of a vehicle clutch

  mobile, device in which it is for the operating member, or cylinder, during startup, to be controlled in such a way that the speed of rotation of the motor remains

  within a preset speed range

  bli located around a variable nominal speed of rotation

  ble depending on the position of the accelerator pedal.

  This imposes stringent requirements on the operation of the operating member, or jack, so that the known control methods do not yet seem to respond to them.

  Starting from this prior state of the art

  re, the present invention aims to improve a process of the kind defined above so that for a minimum consumption of gas under pressure the operating speed can practically be adjusted completely at will with the emphasis on a finely controlled sensitive

  for low operating speeds.

  This object is achieved according to the invention, for a method of controlling an electropneumatic actuating member, or jack, the working chamber of which can be

  communication, by means of two electromechanical valves

  magnetic, either with a vacuum source or with a pressure source, by the fact that, when a slow movement of the operating member, or jack, is required, the two solenoid valves are controlled, by rhythmic pulses, with the same frequency and a pulse rate

variable for each valve.

  In an advantageous embodiment of

  the invention the pulse rates for decay rates

  different placement and for each part of the race

  the operating member, or actuator, are determined, depending on

  tion of control signals in an electronic control unit and transmitted as a control signal,

to the valves.

  In the method of the invention, the control for rapid evacuations or refills of the

  work is obtained with an open valve either directly

  tion of the vacuum source, either in the direction of the pressure source, the other valve being substantially closed,

  that is, for a movement as fast as pos-

  sible open valve is set to maximum flow (sec-

pulse rate).

  According to the invention it is provided for slow movements that the two valves are open so that air

  flows in or out through the now open valve.

  To obtain the displacement the other valve must be open

  longer since at the amount of air performing the de-

  placement is added the quantity of air entering or leaving.

  The available pressure potential is reduced in

  its action inside the working chamber.

  The pulse rate ratio determines the final pressure that can be achieved in the pressure chamber

  work at the end of X pulses, o X, for a given ratio

  born of pulse rates, is inversely proportional to the value of pulse rates. The fact that the two valves are controlled with the same frequency does not exclude that the frequency for determined displacements is variable, that is to say

  can be freely chosen, for example for a

  ment at 50 Hz and for another displacement at 100 Hz The pro-

  assigned allows, for a minimum consumption of gas under pressure, to regulate almost completely at will the

  maneuvering speed with emphasis on a fine command

  sensitive for low operating speeds.

i

Claims (2)

  1 Method for controlling a control unit   electropneumatic work, or jack, the working chamber of which can be brought into communication, by means of two electromagnetic valves, either with a vacuum source or with a pressure source, characterized in that,   when a slow movement of the operating member, or   rin, is required, the two solenoid valves can be com-   mandated, by rhythmic impulses, with the same   variable frequency and pulse rate for each valve.   2 Method according to claim 1, characterized   in that the pulse rates for traveling speeds   different cement and for each part of the course of   the operating member, or actuator, are determined in f onc-   tion of control signals in a control unit   electronic and are transmitted as a signal valve, valves.