FR2468790A1 - Control circuit for variable speed output - compares actual shaft speed with pre-set value to operate pressure regulator for clutch piston - Google Patents

Abstract

The speed of the output shaft of a variable speed output is controlled by a servo-control which takes a signal from its output shaft. The input shaft (1) drives the clutch (2) whose discs are operated by the piston (3) at a controlled pressure. The clutch output shaft (4) transmits the power through a torque converter to the output shaft (6). A proximity detector (7) monitors the actual speed of the transmitter (10), which is compared with a reference value A signal, related to the magnitude of the error, acts on the pressure regulator (9) which in turn controls the pressure on the piston (3) and the speed of the clutch output shaft (4).

Description

i

The present invention relates to devices comprising a-

clutch sliding in front of a hydrocin6ti- torque converter

that intended to vary the ratio between the speed of the shaft

  input of the device and its output shaft.

The present invention relates more particularly to the case where the output shaft is sometimes stopped and where it is necessary to

  get back in motion quickly. For example, in the case of or-

steering gears of a tracked machine as described in the brief

French vet N 75 1C692.

To get the tracked gear fired, you must get a filling

  quick sage of the piston ensuring the compression of the discs of Item-

clutch located in front of the torque converter.

  It is known that to obtain the best result we leave

  residual pressure in the clutch piston, the

ques are thus in contact and ready to work Nlais if this pressure is not very precisely calibrated, one drives more or less quickly the input shaft of the torque converter whose

the output shaft is stopped and unnecessary energy is spent

lost in the hydrokinetic converter and in the end

sliding clutch, -

The value of this lost energy is proportional to the pressure in the clutch control cylinder; But it turns out that these sliding clutches are designed to transmit all of the energy at low pressure,

  this to have a long service life.

It is therefore common that for the value of the energy lost to be low it is necessary to have a pressure on the discs of 0.09

bar, for example, and a corresponding effective control pressure

  laying in the piston (larger area) of 0.03 bar,

for example.

  However, many factors disturb the correspondence between the piston control pressure and the effective pressure transmitted to the discs: return springs, oil pressure losses, leaks, mechanical friction, variations in viscosities, coefficient friction, etc. so much so! It is impossible to set the pressure readjusted to a fixed value without setting it very high, so that the system works with a sure shot. To overcome these drawbacks resulting in a waste of energy, the present invention consists in adjusting the pressure of the clutch so as to have a speed of the input shaft.

from the converter to a given value.

  Indeed, the input torque of the converter, which is the same as that transmitted by the clutch, is proportional to the square of this speed., Its regulation at a low level will give

  assurance that the discs are in good contact since they

put a known couple and that this couple has a low value,

preset and acceptable.

The device, object of the invention, therefore comprises:

  1) a device to measure the speed of the input shaft of the

  vertisseur - 2) a pressure regulator of cormmande of the em-

clutch - 3) a control between these 2 values.

It will be better understood by referring to fig. 1 in the-

which the input shaft 1 drives the clutch 2 whose

  ques are pressed by the piston 3 adjustable pressure.

The output of this clutch drives the shaft 4 which serves as an input to the torque converter 5. The shaft 6 constitutes the output of the system, 4 A speedometer which can be, for example in the form of a detector proximity 7, in front of a wheel

notched 10 provides the input signal of the asserting device

screwing of the control pressure; this signal is compared to

  the reference value and any difference acts on the regulation

pressure tor 9 which by varying the force on the clutch discs accelerates or slows the shaft 4 in order to maintain its

  speed around the preset value.

  The turn generator control device 11, which is also

  their also a pressure regulator, but linked to the steering wheel

  noeuvre, acts in a known manner, in particular in the manner

written in French patent No 75 lC692 already cited above, To avoid any interference between the 2 systems, a valve

check valve 12 isolates the regulation device, object of the pre-

feels a patent, the action of which is required only in the absence of

general turn generator.

The device can be used whenever a dimmer

  of vitesso produced by a hydroclutch and converter

  netic must have a very short response time between stopping and starting, for example for a tracked vehicle direction

Claims (2)

1 - Device allowing the rapid setting in speed of a tree with variable speed controlled by a sliding clutch and a con- hydrokinetic torque converter, characterized in that during the stopping of the output shaft of the system there prevails inside the clutch control piston a pressure whose value is adjusted from of the speed of   the input shaft of the torque converter so as to hand-   keep the clutch discs in contact without dissipating too much of energy. 2 - Device according to claim 1 characterized in that the means used to detect the speed of the shaft is   a proximity sensor providing a signal whose frequency   quence linked to this speed is, after transformation into digital or analog form: s compared to a reference value 'thus providing an error signal constituting an element which leads to a servo which controls the variation of the pressure of the clutch piston.