FR2523675A1 - DEVICE FOR DETECTING THE TEMPERATURE OF AN ELECTROMAGNETIC CLUTCH OF A VEHICLE - Google Patents

Abstract

THIS DEVICE IS SUITABLE FOR DETECTING THE TEMPERATURE OF AN ELECTROMAGNETIC CLUTCH COMPRISING A WINDING 7. THE VOLTAGE APPLIED TO THE WINDING 7 IS MEASURED BY A CIRCUIT 41 OF VOLTAGE MEASUREMENT; AND THE CURRENT CIRCULATING IN THIS WINDING IS MEASURED BY A CIRCUIT 42 OF MEASURE. A DIVIDER 43 IS EXPECTED TO DIVIDE THE VOLTAGE MEASURED BY CIRCUIT 41 OF CURRENT MEASUREMENT MEASURED BY CIRCUIT 42. THE OUTPUT OF THE DIVIDER 43 IS FUNCTION OF THE RESISTANCE OF THE WINDING OF THE CLUTCH, WHICH VARIATES WITH THE TEMPERATURE OF THE THIS WINDING. THE OUTPUT REPRESENTS THE TEMPERATURE OF THE WINDING AND IS COMPARED TO A REFERENCE VOLTAGE BY A COMPARATOR 45. THE OUTPUT OF THE COMPARATOR IS INDICATED IN THE FORM OF AN ALARM.

Description

The present invention relates to a device

  to detect the temperature of a clutch coil for a vehicle, to prevent overheating

of this clutch.

  In electromagnetic clutches: a;

  we know an electromagnetic clutch; powder

  electromagnetic powder clutch comprises a

  ring nut attached to a crankshaft of an engine,

  clutch winding provided in the driving member, a

  mounted organ attached to an input shaft of a box of vi-

  and adjacent to the leading organ with a small

  iron, and a magnetic powder arranged in a chamber of

  the clutch The change of gear in the gear box

  its is effected by operating a shift lever

  The gearshift lever includes a

  switch for the circuit of the winding of the clutch; when the shift lever is grasped by the operator's hand the switch is opened to cut off the clutch current As a result, the change of gear

  report can be made in the gearbox

  that the lever is moved to the engagement position

  of a report, and released by the hand of the operator, the

  switch is closed so that the electric current circulates

  the in the clutch coil to magnetize the drive member When the accelerator pedal is depressed, the

  current applied to the winding increases the magnesium

  The tick is then agglomerated in the air gap between the driving member and the driven member, so that the latter is thus coupled to the driving member. The clutching current flowing in the winding increases gradually as a function of the degree of rotation. depression of the accelerator pedal, while there is a sliding of the clutch between the body

  driving and the driven member, the clutch being progressively

  when the clutch current reaches the non-value Thus the vehicle can be started by depressing

  p Accelerator pedal without activating an accelerator pedal.

  Such a clutch device is

  described in U.S. Patents 3,073,422 and 3,094,202.

  In this electro-agnetic efbrayae, the te: p

  The winding gap increases with increasing clutch current and friction between the drive member,

  the driven organ and the electromagnetic powder In a

  conventional clutch, to detect overheating of the coil

  There is also provided a temperature sensor such as a thermistor on a housing of the clutch. Since this measuring device indirectly detects the temperature of the winding, the thermal sensor produces information on an increase in the temperature of the clutch. winding with a certain delay It is therefore difficult to remedy instantly this temperature defect at

average of the conventional device.

  The object of the invention is to provide a device which directly detects the temperature of the winding of the clutch According to the invention, the current flowing in the winding and the voltage applied to this winding are measured and the resistance of the 'winding is calculated &

  from this measurement Because the resistance of the

  bearing varies with the temperature of the material of this

  a temperature greater than a predetermined value

  completed can be detected by comparing the resistance

with a reference value.

  The subject of the invention is a device for detecting

  the temperature of an electromagnetic clutch of a

  vehicle, the clutch comprising a winding for

  handle the clutch member to engage it, including

  a first measuring circuit for measuring the voltage applied to the clutch winding; a second circuit

  measuring the current flowing in the winding

  : Ient; a divider to divide the voltage measured by the

  first measuring circuit by the current measured by the

  a measuring circuit, a comparator to co-separate the output

  divisor to a reference value; and a warning circuit to indicate the output of the comparator under the

form of a warning signal.

  Other features and advantages of the invention

  will appear in the course of the description which follows,

  made with reference to the accompanying drawings given only.

  by way of example and in which: FIG. 1 is a sectional view of a clutch

  Electromagnetic Powder used with a device

  the invention; Fig 2 is a sectional view along the line Zr Z of Fig 1; Fig 3 is a block diagram of a device

  according to the invention to detect the temperature of the

  brayage; FIG. 4 is a circuit diagram of a mode of

  embodiment of the device according to the invention.

  Referring to Figs 1 and 2 which show an electromagnetic powder clutch to which the invention is applied, this clutch designated by reference 1 is disposed between an internal combustion engine (not shown)

  and a four-speed gearbox 2 which is

  to a final reducing device 3.

  The electromagnetic clutch 1 to powder comprises

  a casing 4, and a driving plate 6 which is connected to the end

  a crankshaft 5 of the internal combustion engine, an annular driving member 8 fixed to the driving plate 6, a clutch winding 7 provided in the driving member 8, and a driven member 10 which is fixed by means of splines. on an input shaft 9 of the gearbox 2, delimiting an airgap 11 with the driving member 8 A magnetic powder is disposed in a c Iha: bre c powder 12 A cap 13 fixed on the driving member S co: mporte a cylindrical portion 13a which is coaxial with the shaft 'entr 9 e, on which are

  fastened slip rings 14 Leaz baues 14 are re-

  electrically connected to the winding 7 to the; oyen of conductors X Brushes 15 applied against the rings 14 are carried by a support 17 and connected by means of conductors

  to a control device which will be described in the following.

  In such an arrangement, the driving plate 6 and the driving member 8 rotate together with the crankshaft 5,

  and the magnetic powder enclosed in the chamber 12 to

  dre is drawn to the inner surface of the driving member 8

  by the centrifugal force When the winding 7 of the em-

  clutch is excited by the current distributed by the conductors

  Y, brushes 16, rings 14 and X conductors,

  the driving member 8 is magnetized to produce a magnetic flux

  The powder is thus agglomerated in the air gap 11 so that the output power of

  crankshaft 5 is transmitted to the input shaft 9 by the in-

intermediate of the clutch.

  Leading gears 18 to 21 of first to fourth report came from material on the input shaft 9 of the

  gearbox 2 The driving gears 18 to 21 are engaged

  respectively engaged with driven gears 23 to 26.

  The gears 23 to 26 are rotatably mounted on the output shaft 22 which is parallel to the input shaft 9 Each of the driven gears 23 and 24 is adapted to be engaged in engagement

  with the output shaft 22 by actuating a synchronizing mechanism

  27, and each of the driven gears 25 and 26 is adapted to be engaged in engagement with the output shaft 22 by means of

  of a synchronizing mechanism 28 in a well known manner.

  In addition a pinion 29 of reverse gear is formed on the arm

  In this way, by operating a currency exchange lever,

  In a gear ratio (not shown) of the gearbox, the gear 23 is coupled to the output shaft 22 by the synchronizing mechanism 27 and the first gear is thus obtained. In a similar fashion, the second, third and fourth gear reports can be obtained respectively in

  Actuating the gear lever.

  In addition, an output pinion 30 is formed on a

  Extremity of the shaft 22 which meshes with a crown den-

  32 of a differential 31 of the final reducing device; The output of the shaft 22 of the gearbox 2 is thus

  transmitted to satellites 36 by means of a car-

  ter 33, a cross 34 and planetary 35 and then

  driving wheels through trees 37.

  Referring to FIG. 3 which shows the device

  according to the invention, the winding 7 of the clutch is

  electrically connected to a voltage measuring circuit 41 and to a current measuring circuit 42.

  two circuits 41 and 42 are applied to a divider 43.

  Output signals from the divider 43 and from a reference voltage generating circuit 44 are applied to a comparator 45. The output of the comparator 45 is applied to a warning circuit 48 via a holding circuit 46 which can be re-armed by means of a circuit

47 of recovery.

  The voltage across the winding 7 of the envelope

  clutch and the current flowing in this winding are measured by the circuits 41 and 42 and the outputs of the two

  circuits are applied to the divider 43 in which is ef-

  performed the operation R = V / I, where R is the resistance, V is

  the voltage and I is the current The resistance of the coil-

  7 of the clutch can thus be obtained.

  this Rt, which varies with the variation of the temperature of the winding, can be written in the form: Rt = R (1 + o LT) where is the coefficient of the material of the winding and T is the time. divider 43 produces an output voltage which corresponds to the resistance Rt The voltage of

  output is compared to a reference voltage in the

  The reference voltage is slightly less than a value which is likely to produce the overheating of the gearbox. The comparator 45 produces an output signal when the input voltage of the divider is greater than the voltage that reference. This means that the temperature of the clutch rises to a value which is close to the superheat temperature. The output signal of the comparator 45 actuates the hold circuit 46 to produce an output which is maintained until a reset signal is applied to it by the recovery circuit 47 The warning circuit 48 operates

  then to produce an indication or a sound.

  FIG. 4 shows an example of a circuit for the device represented in FIG. 3. The voltage applied to the winding is measured by an operational amplifier O P 1 with resistors R 2, R 3 and R 4 and the current is

  measured by an operational amplifier P 02 with resistances

  R 1 and R 5 The output K of the amplifier O P1 and the output L of the amplifier OP 2 are applied to the divider 43 to perform the calculation -K / L to produce a voltage - The output voltage M is compared by the comparator

  OP 7 at a reference voltage applied by the resistors

  these R 10 and R 11 When the output voltage M is higher than

  reference to the reference voltage, the OP 7 comparator

  an output signal which actuates a tilting circuit constituting

  set by NOHN-OR NOR 1 and NOR 2 gates to pass the output to the NOR NOR gate 1 to the high level The high level output of the flip-flop circuit turns a transistor Tr conductive so that a warning light bulb AL is lit If a switch SW is closed, a resistor signal is applied to the flip-flop circuit to cause the output of the flip-flop circuit to go low. The transistor Tr is thus made non-conductive to extinguish.

the AL bulb.

  The invention relates to a device for detecting an electro-imuticean clutch of a vehicle, said clutch comprising a winding for clutching the clutch orifices to encircle the clutch, characterized in that it comprises a first measuring circuit (41) for measuring the voltage applied to said clutch coil (7), a

  second measuring circuit (42) for measuring the current

  forming in said winding, a divider (43) for

  aim at the voltage measured by the first measuring circuit

  (41) by the current measured by the second measuring circuit.

  re (42), a comparator (45) for comparing the output of the

  divider to a reference voltage, and a warning circuit

  sweat (48) to indicate the output of said comrader under

the form of an alarm.

  2 Apparatus according to claim 1, characterized

  characterized in that said second measuring circuit (42) is

  a circuit producing an output voltage corresponding to

  measured current, and said comparator (45) compares the output voltage of the divider (43) to a voltage of

  reference which is slightly lower than a critical voltage

  tick which corresponds to the temperature of overheating of the clutch.

  Apparatus according to claim 2, characterized

  characterized in that it further comprises a holding circuit (46) for holding the output of the comparator (45) and for applying to the warning device (48) an output which is

function of the holding state.

  Apparatus according to claim 3, characterized

  characterized in that the circuit (46) tomorrowtien is constituted by a toggle circuit (NO R1, i4 NO Rf and by a circuit (47)).

recovery from it.