FR2557236A3 - HYDRAULICALLY CONTROLLED FRICTION CLUTCH AND MOTOR VEHICLE DRIVE UNIT USING THE CLUTCH - Google Patents

Abstract

THE INVENTION RELATES TO A HYDRAULICALLY CONTROLLED FRICTION CLUTCH, USABLE IN THE DRIVE GROUP OF A MOTOR VEHICLE. THE CLUTCH INCLUDES AN ACTUATION CYLINDER 26 THAT CAN ROTATE WITH THE INPUT ELEMENT 28 OF THE CLUTCH 20 AND OF WHICH THE PUSH CHAMBER 36 IS CONNECTED TO A PRESSURIZED LIQUID DISTRIBUTION CIRCUIT AND TO A DISCHARGE CIRCUIT; THE DISCHARGE CIRCUIT INCLUDES AN INTERCEPTION VALVE 76 NORMALLY OPEN, WHICH CAN ROTATE WITH THE ACTUATION CYLINDER 26 AND CLOSED BY CENTRIFUGATION.

Description

FRICTION CLUTCH HYDRAULICALLY CONTROLLED AND

  MOTOR VEHICLE DRIVE GROUP USING

THIS CLUTCH

  The present invention relates to hydraulically controlled friction clutches for coupling an input rotating member coaxially with an output rotating member to rotate with each other.

  In particular, the invention relates to an em-

  friction clutch of the type in which the element

  and the output member are provided with respective alternating coaxial friction disks which can be applied axially against each other by means of the hydraulic control, and wherein said control

  hydraulic system comprises an actuating device

  formed by a cylindrical body rotatably connected to the input member and in which a

  piston directed towards said disks, the piston defined

  with the cylinder a thrust chamber, and in which there is provided a hydraulic control circuit comprising a source of pressurized liquid, a supply means for introducing the pressurized liquid into said thrust chamber and a discharge means serving to evacuate the liquid from the thrust chamber and having an interception valve normally

  open, rotatable with the actuator

  hydraulically operated and centrifugally

closing condition.

  The object of the invention is to create a friction clutch of the type defined above, a simple and robust construction and able to operate in a safe and fully automatic manner in relation to the

  rotational speed of the input element.

  This problem is solved in that in the cylindrical body of the hydraulic actuator is

  formed a discharge passage with an ori-

  radially, and in that the interception valve comprises a seat formed in said radial portion of the discharge passage and a centrifugal feeder slidable in said radial portion between the seat of

  valve and the axis of the hydraulic actuator

  that by carrying a shutter cooperating with said valve seat; said centrifugal weight being dimensioned and positioned in such a way that the

  closing stroke of the valve shutter

  terception begins when the rotational speed of the input element is of the order of 1000 rpm and is completed when the rotational speed of this element

  input is of the order of 2500 rpm.

  According to other features of the clutch con-

  form to the invention: 1. The discharge passage communicates, downstream of

  the interception valve, with a lubricating chamber

  cation for friction discs.

  2. The valve plug is tapered.

  3. Valve shutter is spherical.

  4. Centrifugal Lamasselotte is spherical and

  itself the valve shutter.

  5. The clutch is mounted on a drive group

  of a motor vehicle comprising an engine, a gearbox and a differential and is disposed

  between the gearbox and the differential, its

  the input shaft being coupled to the output shaft of the

  gearbox and its output element being accom-

differential.

  6. The clutch is mounted in a drive group

  of a motor vehicle comprising an engine,

  a gearbox and a differential and it is dis-

  placed between the engine and the gearbox.

  In particular, the friction clutch according to the invention is advantageously applicable to motor vehicle drive units comprising a motor, a gearbox and gearboxes.

  staggered or gradual, and a differential.

  In this application, the clutch according to the invention can be used for the connection between the

  output of the gearbox and the input of the differential

  tiel, or also for the connection between the motor output shaft and the input shaft of the gearbox. The second arrangement is preferred, particularly in the case where a gearbox with change of

  gradual speed is used, since with this arrangement

  In this case, the friction clutch is engaged depending on the speed of rotation of the engine with the gear selector while the clutch is released depending on the speed of the vehicle.

  the speed of rotation of the input element of the

  ential. Consequently, when the vehicle slows down, the friction clutch according to the invention behaves

  in a similar way to a "blocking element", independent of

  the ratio of the gearbox and the speed of rotation of the motor. During rapid vehicle braking, the drive controller is locked in a gear other than the minimum gear ratio, thus preventing the risk of damaging the drive.

  proper and a difficulty in restarting the vehicle

cule.

  Other features and advantages of the invention

  will be highlighted in the rest of the description.

  tion, given by way of non-limiting example, in

  in the accompanying drawings, in which: FIG. 1 is a diagrammatic sectional view.

  partial drive of a self-driving vehicle

  mobile, comprising a friction clutch according to the invention;

  FIG. 2 represents on an enlarged scale a first

  first variant of a detail of the clutch; Figure 3 shows an enlarged scale a second variant; FIG. 4 represents on an enlarged scale a third variant; and Figure 5 is a graph illustrating the characteris-

  functional feature of the friction clutch.

  FIG. 1 schematically represents a drive unit for motor vehicles, comprising an internal combustion engine 10 whose shaft 12 is connected to the input shaft 14 of a gearbox 16

  having an output shaft 18 coupled, through the

  a friction clutch 20, a differential 22 which drives the half-shafts 24 of the driving wheels.

of the vehicle.

  The gearbox 16 may be of the type

  staggered speed or gradual variation of speed. In the second case, it can be constituted by an expander of the type with expandable pulleys

  or by an epicyclic variator with

conical planetary gnons.

  The friction clutch 20 comprises a flywheel or cylindrical body 26 formed by an annular element 28 coupled to rotate with the output shaft 18 of the gearbox 16 and having a radially inner axial portion 30 and an axial portion

  radially outside 32 between which can be de-

  place an enclosed annular piston 34. The inner face

  of the annular piston 34 defines, with the cylindrical body

  28, a thrust chamber 36 and is subjected on its opposite side to the action of an elastic member, constituted in the example shown by a cup-shaped spring 38, which tends to push the piston

34 against the cylindrical body 28.

  The outer axial portion 32 of the cylindrical body

  28 carries an annular skirt 40 in which are dis-

2557236.

  laid several annular friction discs leading

42 being able to slide axially.

  Reference numeral 44 denotes a gear coaxially rotatably supported on output shaft 18 of gearbox 16 and engaged with

  a ring gear 46 formed on the housing of the differential

  22. The ring gear 44 has a projection

  axial bead 48 extending in the direction of the body

  cylindrical 28 and carrying a series of annular disks.

  driven friction rests 50 that can slide axially

  and inserted in the driving discs 32.

  The thrust chamber 36 is connected to a hydraulic supply circuit comprising one or more passages 52 formed in the axial portion 30 of the cylindrical body 28 and communicating, via radial passages 54 and an axial passage 56 formed in the shaft 18, with a power supply and control unit 58. The unit 58 comprises a two-position control valve 60 of the "on-off" type of known type, normally of the type comprising a proportional electric control, which allows to selectively distribute oil from a collection tank 62 to the conduit 56 via a hydraulic pump 64 or to cut this supply by connecting the conduit

56 to the reservoir 62.

  In the cylindrical body 26, there is provided a

  discharge geometry having a radially axial section

  66 formed in part 28 near the

  32, a radially inner axial section 68 formed in the axial portion 30 and a radial section

  which connects the axial sections 66 and 68.

  The end of the axial section 68 which is opposite

  at the radial section 70 opens into an annular chamber

  70 defined between the axial portion 48 of the gear

  44 and the axial portion 30 of the cylindrical body 26 and communicating with the zone containing the friction discs 42 and 50 via radial passages

  lubrication 74 formed in the projection 48.

  In the radial section 70, a valve is provided

  interception designated as a whole by 76 and

  taking a seat 70 which cooperates with a shutter 80 carried by a centrifugal feeder 82 which can slide freely inside the radial section 70 between the seat 78 and the axial part 30 of the cylindrical body 28. In the example shown, The valve plug has a conical shape and the centrifugal feeder 82 has a series of peripheral axial grooves 84

for the passage of oil.

  The centrifugal weight 82 is arranged and sized

  sioned so as to ensure a gradual closure of the seat 78 by the valve plug 80, thereby cutting the communication between the thrust chamber 36 and the chamber 72 when the speed of rotation of the shaft 18, and therefore the body cylindrical 26, exceeds

  a predetermined threshold value.

  We will now describe in the following the function-

  friction clutch 20.

  Actuation of the friction clutch 20 is

  controlled, during the running of the engine 10, through

  the distributor "on-off" which is controlled by means of a conventional selector lever actuated by

  the driver. When this lever is positioned in the posi-

  neutral position, the distributor 60 is placed in a position

  closing communication so that the communication between the pump 64 and the conduit 56 is interrupted while the communication between the conduit 56 and the discharge 62 is open. In this condition, oil can

  to be in the thrust chamber 36 is not

  -7 put at a static pressure and it goes out, through an automatic ball valve 86 of conventional type which is mounted in the piston 34, being collected in the reservoir 62. The friction discs 42 and 50 are therefore completely free so that the output shaft 18 of the box of

  speeds 16 is uncoupled from the differential 22.

  When the selector lever is placed in the

  forward or reverse, the distribution of

  60 is placed in the open position in

  thus smoothing a communication between pump 64 and

  56. Pressurized oil is then

  through the radial passages 54 and

  passages 52 into the thrust chamber 36.

  In the idling condition of the engine 10, or when the output shaft 18 of the gearbox 16 rotates at a speed lower than the calibration value of the valve 76, oil sent into the chamber 36 becomes discharging through passages 66, 70 and 68 into chamber 72 so as to lubricate friction discs 42 and 50 in the period in which they slide

relative to each other.

  During an increase in the speed of rotation of the motor 10, and consequently of the output shaft 18 of the gearbox 16, the centrifugal weight 82 tends to move radially outwards, thereby closing progressively the shutter 80 against the valve seat 78. Accordingly, the oil pressure in the thrust chamber 36 increases gradually by bringing the piston 34 of the disks

  of friction 42 and 50 until they are complete-

  applied against each other.

  When the valve 76 closes completely, the pressure necessary for the complete engagement of the clutch 20 is established in the thrust chamber 36 while the lubrication of the disks 42 and 50 is obviously interrupted, causing their mutual blocking. When the speed of the cylindrical body 26 again decreases below the threshold value, the valve 76 opens gradually, producing again a

disengaging the clutch 20.

  In the case of the friction clutch 20 shown in the example of Figure 1, where the gearbox

  16 is of the type with gradual variation of speed, the

  friction clutch 20 has a "green" type behavior.

  "independently of the ratio of the converter 16 and the rotational speed of the motor 10. In fact, well

  that the engagement of the clutch 20 is effected

  the speed of rotation of the motor 10, while the variator 16 is in a small ratio, a

  disengagement occurs depending on the speed of the vehicle

  and, in fact, it is clear that this speed corresponds to a defined angular speed of the differential housing 22 and consequently of the element.

output 44 of the clutch 20.

  The operation of the friction clutch 20 in such conditions is shown in the graph of FIG. 5, where the rotational speed of the motor 10 for the small ratio of the variator 16 and the speed of the vehicle respectively has been plotted on the abscissa. the torque transmitted by the clutch 20 has been plotted on the ordinate. As can be seen, the engagement start of the clutch

  As an example, it occurs at a rotation speed

  the engine 10 approximately equal to 1000 rpm and the en-

  full shutdown occurs at approximately 2500 rpm, while the clutch starts at a

  vehicle speed of approximately 16 to 17 km / h and is ter-

  mined at a speed of about 7 to 8 km / h. As we can

  see it, the engagement characteristic of the clutch

  age 10 is extremely gradual and progressive and she

  is similar to that of conventional centrifugal clutches

mechanical type.

  It is, of course, obvious that the clutch

  friction 20 could be used in a different way.

  of the one illustrated and described above and

  For example, it could be interposed between motor 10 and

  the gearbox 16. However, in this case the

  clutch would obviously be sensitive to the rotational speed of the motor 10 and therefore unintentional disengagement of the clutch could be performed at low speeds of rotation of the motor 10, with the

  gearbox 16 placed in a big report.

  In addition, it is necessary to note that the valve

  Interception 76 may have different configurations

  of the one illustrated in FIG. 1 and could for example be of the type illustrated in the variants

Figures 2 to 4.

  In the case of Figure 2, the axial passage 68 does not exist and the passage 66 is connected to a discharge side outlet 87 adjacent to the valve seat

  78. Valve shutter 80 and centrifugal feeder

  82 have in this case a conformation similar to

that of Figure 1.

  In the case of FIG. 3, the valve shutter 76 is constituted by a ball 88 coming to bear against the centrifugal weight 82 while in the case of FIG. 4, the centrifugal weight is

  constituted by a ball 90 adapted to serve equally

shutter valve.

  Of course, the invention is not limited to the embodiments described above and shown, from which we can provide other modes and other embodiments, without out

of the scope of the invention.

Claims (11)

  1. A hydraulically controlled friction clutch for rotatably coupling an input rotary member with a coaxial output rotary member, particularly for motor vehicle drive units, where the input element and the output element are provided with coaxial friction discs   respective alternating which can be applied axially-   against each other by means of the hydraulic control   in which said hydraulic control com-   takes an actuating member constituted by a cylindrical body rigidly connected to rotate with the input member of the clutch and in which the piston directed towards said disks is slidable, said   piston defining with the cylinder a chamber of   and a hydraulic control circuit comprising   a source of liquid under pressure, a means of   for supplying pressurized liquid to said thrust chamber, and a discharge means for discharging the liquid from the thrust chamber,   said discharge means comprising an interception valve   normally open ception which can rotate with the hydraulic actuator and which is actuated   by centrifugation in the closed condition,   in that in the cylindrical body (28) of the disc   positive hydraulic actuator (26) is formed a discharge passage (66, 70, 68) having a radially oriented portion (70), and in that the interception valve (76) comprises a seat (78) formed in said radial portion (70) of the discharge passage and a centrifugal feeder (82, 90) slidable   in said radial portion (70) between the seat of   pope (78) and the axis of the hydraulic actuator   plate (28), and carrying a shutter (80, 88, 90)   with said valve seat (78); It   centrifugal burbot (82, 90) being dimensioned and posi-   in such a way that the closing stroke of the shutter (80, 88, 90) of the interception valve (76) starts when the rotational speed of the input element (18) is order of 1000 rpm and be terminated when the rotational speed of this element   input (18) is of the order of 2500 rpm.   Clutch according to Claim 1, characterized in that the discharge passage (66, 70, 68) communicates, downstream of the interception valve (76), with a   lubrication chamber (72) for the silver discs. tion (42, 50).   Clutch according to claim 1, characterized   in that the valve plug (80) is tapered.   4. Clutch according to claim 1! characterized   in that the valve plug (88, 90) is spherical.   5. Clutch according to claim 1, characterized in that the centrifugal weight (88) is spherical   and itself constitutes the valve plug.   6. Clutch according to claim 1, characterized in that it is mounted on a drive unit of a motor vehicle comprising a motor (10), a gearbox (16) and a differential (22), its element inlet (26) being coupled to the output shaft (18) of the gearbox (16) and its output member   (48, 44) being coupled to the differential (22).   Clutch according to claim 1, characterized in that it is mounted in a drive unit of a motor vehicle comprising a motor (10), a gearbox (16) and a differential (22) and is arranged   between the engine (10) and the gearbox (16).   8. Drive unit for a motor vehicle, comprising a motor, a gearbox connected to the motor shaft and having an output shaft, a differential connected to the gearbox, and a clutch   hydraulically controlled friction according to one or more   of claims 1 to 7 and interposed between   motor and the differential, characterized in that the   friction clutch (20) is associated with a compression unit   mandrel (58) comprising a distributor (60) movable between a working position in which it allows the pressurized fluid supply of the friction clutch (20) and a closed position in   which power is cut off.   9. Drive unit according to claim 8, characterized in that the friction clutch (20) is mounted between the gearbox (16) and the differential (22). 10. Drive unit according to claim 8, characterized in that the friction clutch (20) is interposed between the motor (10) and the gearbox (16). 11. Drive unit according to claim 9 or claim -10, characterized in that the gearbox (16) is constituted by a variable speed drive.