FR2698053A1 - Servo-positioning drive particularly for a friction clutch of a motor vehicle or a gearbox of a motor vehicle. - Google Patents

Abstract

For a friction clutch, a motor vehicle gearbox, a positioning servo drive with an electric motor (3) and, in a gear case (1), a spur gear (5) are proposed. comprising two toothed wheels (15, 33) with parallel axes. The first toothed wheel (15), made in the form of a toothed sector, makes it possible to actuate a clutch, in particular by means of a crank mechanism (7) and a hydraulic master cylinder (9) . The second toothed wheel (15), in engagement with the first, is located directly on the shaft of the electric motor (3) and has a maximum of seven teeth; it is advantageously made in one piece with the shaft of the electric motor (3). The two toothed wheels (15, 33) are helical toothed wheels, in particular involute. Application for actuating automatic clutches of motor vehicles.

Description

Servo-drive positioning especially for a clutch to

  friction of a motor vehicle or gearbox of a motor vehicle

  The present invention relates to a servo

  positioning drive in particular for a friction clutch of a motor vehicle or a box

  of a motor vehicle.

  Positioning Servo Drives for Automatic Motorized Friction Clutches Must Meet a Wide Range of Requirements This is how the positioning servo drive must be relatively compact in order to fit into the vehicle, including when space is limited To overcome the main clutch spring, the positioning servo drive must be able to generate relatively high actuating forces and disengage the clutch in as short a time as possible. to obtain

  large actuating forces with a servo

  positioning drive driven by an electric motor, thanks to a large multiplication ratio of a multiplication mechanism mounted between the electric motor and an output member, for example a hydraulic transmitter cylinder, or a mechanical transmission member, however, it is necessary find a compromise between the importance of the multiplication ratio and the power of the engine, because the disengagement must be able to be carried out with a high speed of displacement The requirement of a compact construction and the cost factor limit the size of the electric motor to Also use the quality

  setting of a control circuit positioning the servo

  positioning drive for the clutch requires that there are only relatively small tolerances in the drive chain between the electric motor and

the output member.

  Document DE-A-37 06 849 (US-A-4,852,419) discloses an electric motor positioning servo drive for a motor vehicle friction clutch, in which the hydraulic emitter cylinder is driven by an electric motor, by means of a worm gear The worm gear comprises a tangent wheel located between two support bases and mounted thereon, by means of rolling bearings or sliding bearings, which tangential wheel meshes with an endless screw, on the same axis as the motor shaft, the electric motor attached to the gear case The tangent wheel is at the same time part of a crank mechanism with a pusher mounted eccentric to the rotation axis of

  the tangent wheel, actuating the piston of the emitter cylinder.

  In this known positioning servo-drive, a spring is used to reinforce the output torque of the electric motor, which is used as a spring-force accumulator, which amplifies the torque of rotation of the tangent wheel in its movement, in the direction of the disengagement of the friction clutch A sufficiently high speed of movement in the disengagement direction is thus obtained, despite a relatively small sized electric motor. The spring of the spring force accumulator is in the end position of the clutch. tangential wheel, located towards the engaged position of the friction clutch, in a position beyond the dead point and thereby blocks the positioning servo-drive in this end position With the aid of the Although the screw gearing can be used to obtain sufficiently high multiplication ratios, the efficiency of the worm gear is relatively small and the clearance of the gear wheels of the spindle The screw gear is also not small enough for a large number of applications. The object of the invention is to overcome the drawbacks of a positioning servo-drive of the

  aforementioned type and in particular to produce a servo

  electric motor positioning drive for a motor vehicle friction clutch that performs better than conventional positioning servo drives. The invention starts from a positioning servo-drive which is particularly suitable for a friction clutch of a motor vehicle having the following characteristics: a gear case with a first support base and a second removable support base on the first support base, a first toothed wheel, in particular in the form of a gear sector, located between the two support bases, mounted so as to rotate about a first axis of rotation on the two support bases, a second toothed wheel, meshing with the first gear, mounted to rotate about a second axis of rotation, on the gear case, an electric motor driving the second gear, fixed on the gear case, an output member, in particular hydraulic, designed in the manner of a transmitter cylinder, enclosing a piston guided in translation and an output mechanism, in particular in the form of a mechanism cranked to the first toothed wheel and converting its rotation into a translation at least substantially similar to that of

the output member.

  The improvement according to the invention of the positioning servo-drive is characterized in that the first gearwheel and the second gear are helical gears, in particular with involute teeth, in that the second axis of rotation is parallel to the first gear. axis of rotation and in that the second gearwheel has a maximum of seven, in particular

at most three teeth.

  The second gear wheel, forming a pinion, has a very small number of teeth, between one and seven, compared to conventional straight-wheel gears. The first gear, on the other hand, has at least twenty teeth, for example seventy teeth referred to an entire circle, so that it is possible to obtain multiplication ratios comparable to a worm gear. Wheels with straight wheels and a reduced number of gear teeth are described for example in VDI-Zeitung 107, 1965, No. 6, pages 275 to 284 Compared with screw gears with the same multiplication ratio, they

  have a better transmission efficiency.

  positioning drive can therefore be built more compact and / or equipped with a smaller electric motor,

  according to the importance given to the demands placed on it.

  The play of the gears can also be kept very small, so that using the positioning servo-drive according to the invention it is possible to obtain improved adjustment characteristics of a

  positioning adjustment circuit.

  The very small number of teeth of the second gear, used as a pinion, conditions a relatively small diameter of the shaft bearing the toothing of the second gear. In practice, this means that the diameter of the shaft in the area of the gear bottom of the toothing is only a few millimeters, for example 3 mm, so that the support of the second gear must meet high requirements if one wants to avoid arrows, bending stresses and a set of gear wheels that are too high The second gear wheel, which is preferably made in one piece with, and directly in the motor shaft of the electric motor, must be mounted on both sides of the first gear wheel, on the housing

  gears or on a connected part centered with that

  In particular, on the remote side of the engine, the shaft forming the second gear wheel must be mounted as close as possible to the first gear wheel. Since, in general, the helical gearing has end zones. not usable, because of its manufacturing process, for the engagement of the toothing, in the conventional front wheel teeth, the bearings are located axially outside the toothed zone To keep the free length of the tooth weakened shaft by the toothing of the second gear, it is provided, in a preferred embodiment in which the toothing of the second gear is made in one piece with a shaft connected on one side with the electric motor, that of the two bearings supporting the shaft axially, on both sides of the first gear wheel, on the gear case, at least the axially remote bearing of the motor The trestle rests on a bearing of the shaft, axially covering at least part of the toothing. Advantageously, the two bearings rest on bearing surfaces of the shaft, axially covering the toothing thereof. The bearing surface remote from the electric motor preferably has a diameter which is smaller than the diameter of the outer circle of the second gear, that is to say that it is made by machining around the shaft The bearing close to the electric motor is preferably based on a sleeve surrounding the shaft, whose inner diameter is greater than the diameter of the outer circle of the second gear wheel In this way the two bearings can be

  mounted without the teeth being damaged.

  The first gear wheel, coupled with the output member, is mounted axially on both sides in two support bases made separately from one another, but fixed centrally to one another. provided for the second gearwheel in the two support bases, as is customary b in conventional straightwheel gears. But it has been found that a clear improvement can be obtained

  operating characteristics of the servo

  positioning drive, if the second gear wheel is mounted on both sides of the first gear wheel and in the vicinity thereof, in bearings whose centering surfaces are provided jointly on the first gear base, on the same next to the first gear base, in particular on the side facing away from the second gear base. This has the advantage that the two centering surfaces, determining the centering of these two bearings, of the first gear base, The gears can be made with a single clamping of the workpiece, which considerably reduces the tolerances of the centering of the bearings. In embodiments in which the second gear is made in one piece with the shaft. of the electric motor, the range of the electric motor and the range of the bearing remote from the motor are in this case made with a single clamping of the workpiece. previously described manufacture of the staves allows to use, for supporting the second gear, the bearings provided anyway in the housing of the electric motor to support the motor shaft, including when the fact that the motor shaft is supported at less in three points he

  results from hyperstatic support characteristics.

  The amplitude of rotation of the first gear is normally limited in an end position of

  race in particular the end position corresponding to

  laying in the disengaged position of the friction clutch, by a stop placed on the first gear base,

  in the path of rotation of the first gear.

  The stop is preferably removably mounted on the first gear base, so as to allow as simple as possible the mounting of the first gear, when, as explained above, the centering surfaces are provided jointly on the first support base, to support the second gear In this way it is possible to use integral pins of the first gear, on which can be coupled a distance sensor, outside the gear case In a particularly mechanically stable configuration, the abutment is in the form of a finger extending between the first and second basoe- gear, in parallel

at the first axis of rotation.

  In the case of gears with straight wheels, which are not subject to wear, one of the two gears is normally made of a wear-resistant material, for example a plastic material, while the other gear wheel may possibly be In the case of plastic toothed wheels, however, tolerances can be increased to shorten the service life due to plastic deformation of the gearing. The spur gears in which the two gear wheels are The steel or steel pinion and the associated wheel made of bronze or cast iron have improved service life characteristics. Conventional straight-wheel gears of this type, however, rotate in an oil bath. In a preferred embodiment of the invention, the first and the second gearwheels are made of steel or bronze, but unlike conventional straight-wheel gears, they rotate ns a fat filling of the crankcase

  This is where the servo is used.

  Positioning drive operates only intermittently, so that despite the reduced lubrication characteristic compared to oil lubrication, fat filling, one gets a lifetime

  greater than that of plastic teeth.

  While the screw gear of the servo

  Conventional positioning drive may have self-locking properties, positioning servo drives according to the invention with an oblique gear and a very small number of teeth normally do not have self-locking properties To prevent unintentional movement of the servo drive of positioning in its end-of-stroke positions, in particular the end-of-stroke position maintaining the fully engaged friction clutch, in which the electric motor is not energized, it is provided in a preferred variant that at the first gear wheel are associated stop means which block it in at least one of its end positions, in particular the end position position fully engaging the friction clutch The stop means can in this case act directly on the first gear wheel, but also on a

  driving or driven element connected to the gear wheel.

  The stop means may be a spring, clamped between the gear case and the first gear wheel, which locks the first gear wheel in a position of exceeding the neutral position. In addition or alternatively, the stopping means can comprise also a spring latching device, hooking the first gear in the end position by

compared to the gear case.

  While the above stop means locks the first gear, in a manner controlled by its rotation, in a variant there are provided stop means which are controlled by external control devices. These stop means can comprise for example a controlled locking device, blocking the first gear in its end position relative to the gear housing, which locking device is actuated for example according to the command also controlling the electric motor A locking device of this type may comprise an electromagnetically or hydraulically actuated locking latch which locks the first gear wheel or a driven member therewith with respect to the gear housing. But the locking device may also comprise a blocking valve. commanded at the exit of the transmitter cylinder, by which the

  Pressure chamber of the transmitter cylinder can be closed.

  Various other features and benefits

  of the invention are apparent from the detailed description which

  Following An embodiment of the invention is shown by way of non-limiting example in the accompanying drawings. Figure 1 is a top view partly in section of a positioning servo-drive for a friction clutch of a motor vehicle, the cover and the second support base of its gear case being removed;

  FIG. 2 is a sectional view of the servo

  positioning drive along the line II-II of Figure 1;

  FIG. 3 is a detailed view of the servo

  positioning drive, along the line III-III of Figure 1 and Figure 4 is another detail view of the positioning servo-ment, along the line

IV-IV of Figure 1.

  Figures 1 and 2 show a servo

  electric motor positioning drive for a friction clutch of a motor vehicle, comprising a gear case 1 and an electric motor 3, flanged on the gear case 1, which actuates, via a gear with straight wheels 5 and a crank mechanism 7, a hydraulic emitter cylinder 9 whose pressure chamber 11 is connected, by a hydraulic pipe 13, to a not shown cylinder receiver, actuating the disengagement device of the friction clutch electric motor 3 is controlled, in a manner known per se, by an electronic control, actuating the friction clutch when starting and changing

  speed of a gearbox of the motor vehicle.

  The spur gear 5 is a spur gear with involute helical gearing and comprises a first gear 15 in the form of a gear sector, which is rotatably mounted about an axis of rotation 27, one side in a bearing 19 of a first housing shell 21, forming a first support base, and the other in a bearing 23 of a bearing cover, forming a second support base The bearing cover 25 is fixed centered, by screws 29, on a bearing surface 31 of the casing shell 21 The toothed wheel 15 meshes with a toothed wheel 33, designed as a pinion, which is made in one piece with a motor shaft , designated 35, carrying the rotor 37 (Figure 2) of the motor

Electric 3.

  The crank mechanism 7 comprises a pusher 39 which, with one of its ends, is articulated on a crank pin 41 of axis parallel to the axis of rotation 27 of the toothed wheel 15, substantially diametrically opposed to the toothed sector of the toothed wheel, and which at its other end is supported in a cavity of a piston 43 of the emitter cylinder 9 The pin 41 is held between two flanges 45 riveted at 44 on the gear wheel 15 The crank mechanism 7 converts the rotation of the toothed wheel 15 in a movement substantially of

  translation of the pusher 39 and therefore of the piston 43.

  While the toothed wheel 15 has at least twenty teeth, preferably about seventy teeth relative to a complete circle, the toothed wheel 33 serving as a pinion has a number of teeth of between one and seven at the most, preferably between one and three and in particular only two teeth 47 (FIG. 3). In this way it is possible to obtain a multiplication which makes it possible to use a relatively small electric motor for the small dimensions of the spur gear 5. The diameter of the bottom circle defining the bearing cross-section of the drive shaft in the area of the teeth 47 is relatively small and is only about 3 mm in a practical embodiment. To avoid excessive bending stress of the motor shaft 35 in this area, the toothed wheel 33 is mounted centered with respect to the casing shell 21, on both sides of the toothed wheel 15, respectively in a bearing 49 and 51 While the bearing 49 is designed to in the manner of a fixed bearing, radially and axially fixing, in the usual way, the drive shaft 35 at its outlet end of a crankcase 53, the bearing 51 is designed in the manner of an axially free bearing and rests in a seat 55 of a bearing support 57, formed in one piece on the casing shell 21 The bearing 49 is centered in the crankcase 53 which in turn is centered on a bearing surface 59 of the crankcase 21 The staves and 59 of the two Yards 49 and 51 are accessible from the same side of the housing shell 21 so that they can be machined in a crankcase blank in one operation by means of a machine tool. In this way, the bearing 49 supporting the drive shaft 35 in the crankcase 53 can, with another bearing 61, be used as an accurate bearing, thus ensuring that the bearings 49, 51 are centered in a very precise manner. pinion, even if the mounting of the motor shaft 35 in three bearings is hyperstatic. The bearings 49, 51 are very close to the toothed wheel 15 To enable this, the bearings 49, 51 cover the end zones of the teeth grooves, resulting from the manufacture, visible at 63. The bearing 51 rests here on a bearing surface 65, at the free end of the motor shaft, of reduced diameter relative to the diameter of the outer circle of the toothed wheel 33, while the bearing 49 rests on a sleeve 67 pressed on the drive shaft 35, whose inner diameter is equal to or greater than the diameter of the outer circle of the toothed wheel 33 and is fixed axially without circlips on the sleeve 67 and thus on the drive shaft 35 The bearings 49, 51 can be placed thus one after the other on the engine shaft.

  In the position now the friction clutch-

  When engaged, the toothed wheel 15 comes into contact with a finger 73 secured to the casing, acting as a limit stop, via a buffer 71 having the elasticity of the rubber, held in a cutout 69 of the toothed wheel. As shown more particularly in FIG. 4, the stop finger 73 is firmly pressed inside the housing 21, while it is slidably centered in a bore 75 of the bearing cover 25, so that if necessary it can be removed by means of a tool When the stop finger 73 is removed, the toothed gear 15 in the shape of a sector, turned towards the bearing extension 57, can thus be inserted with its fixed axis 17 in the bearing 19, before coming into engagement with the toothed wheel 33, by

return rotation.

  The toothed wheels 15, 33 are made of steel, the toothed wheel 15 may also be made of bronze, and rotate in the casing shell 21, in a grease filling not shown. The casing shell 21 is closed, on its open side. by a casing cover 77 (FIG. 2) which also covers a casing chamber 81 separated from the gear chamber, containing an electronic circuit 79 and in particular also a terminal stage for the operation of the electric motor 3 A connector intended for the connection of the electronic circuit 79 is indicated in 83 The electronic circuit 79 comprises a distance sensor 85, for example in the form of a potentiometer, fixed on the bearing cover, which is secured in rotation with the axis 17, but free axially The distance sensor 85 is

  also housed, protected, inside the cover 77.

  Between a further crank pin 87 of the crank mechanism 7 and a pivot bearing 89 on the crankcase 21 is compressed a spring force accumulator 91, which enhances the driving torque of the electric motor 3 during the movement of the push-button 39, during actuation of the emitter cylinder 9, that is to say in the disengagement direction. The spring-force accumulator 91 is tensioned again upon the return of the electric motor 3, aided in this case by the main spring of the clutch In the end position, associated with the clutch position, of the crank mechanism 7, in which the toothed wheel 15 bears against the stop finger 73, the force accumulator The spring 91 is in a neutral position in which the action line of the spring force accumulator 91 is inclined with respect to the connecting line of the axis 17 with the axis of rotation 27. , opposite the race area The spring force accumulator 91 thus provides, in the clutch position, a blockage of the positioning servo-drive, including when the electric motor 3 n It is understood that instead of the spring force accumulator 91 it is possible to provide a spring which causes only the blocking, in particular a spring.

  overtaking spring of neutral.

  Locking in the clutch end position can also be effected by other means

  stopping, for example with a sensing snap spring

  U-shaped, shown at 95 in FIG. 1, which is raised in the clutch end position on the stop finger 73. The snap-in spring 95 surrounds the buffer 71 and is inserted therewith into the cutout 69 of the

gear wheel 15.

  Another variant of a stop means is shown in FIG. 2, in the form of an electromagnetic locking device 97. The locking device 97 comprises a locking lock 101 guided on the casing shell 21, pre-stressed by a spring 99 in a position of cooperation with the crank mechanism 7 or the toothed wheel 15, which locking latch automatically locks the crank mechanism 7 in the engaged position If for the disengagement, the motor 3 is started up, an electro- At the same time, the magnet 103 excites the locking device 97 and releases the drive. It is understood that instead of the electromagnetic actuation drive of the locking device 97, it is also possible to provide a pneumatic actuation drive. or hydraulic, provided that suitable sources of pressure are available. As an actuating drive, it is also possible to use the electric motor 3, of any type. existing, for example by providing that the locking latch is prestressed, elastically, in its engagement position and is released by a driven cam angularly offset with the wheel

toothed 15.

  FIG. 1 shows another variant of a stop device in the form of an electrically controlled actuating or locking valve 105 mounted at the outlet of the emitter cylinder 9 in the hydraulic line 13, and which at the state not excited, closes the connection of the emitter cylinder with the receiver cylinder and is also excited, when the electric motor 3 is excited, which releases the connection between the emitter cylinder and the receiving cylinder When the valve 105 is closed, the hydraulic volume retained in the pressure chamber It keeps the servo-drive positioning in the

  clutch end position.

  The toothed wheels 15, 33 are straight wheels with involute helical teeth. The reduced number of teeth of the toothed wheel 33 determines a relatively small overlap of profiles which is, however, advantageously compensated by a large recovery ratio, which gives in the together a good total overlap factor, the large helix angle which is preferably about 300 or more causes only very low gearing noises.

  profile preferably have a normal modulus of about 1.25.

  The profile offset also serves to reduce the bending stresses in the case of a very small pinion 33 by increasing the cross sectional area of the beam.

pinion.

Claims (18)

  1 positioning servo-drive, in particular for a friction clutch of a motor vehicle or a gearbox of a motor vehicle, comprising a gear case (1) with a first support base (21) and a second support base (25) removably mounted on the first support base (21), a first gear (15), in particular in the form of a gear sector, located between the two support bases (21, 25) mounted to rotate about a first axis of rotation (27) on the two bearing bases (21, 25), a second gear (33) meshing with the first gear ( 15) rotatably mounted about a second axis of rotation on the gear case (1), an electric motor (3) driving the second gear (33) fixed to the gear case (1),   an output member (9, 39), in particular hydraulic, designed in the manner of a transmitter cylinder (9), enclosing a piston (43) guided in translation and an output mechanism (7), in particular in the form of a crank mechanism connected to the first toothed wheel (15) and converting its rotation into a translation at least substantially similar to that of the output member (9, 39), characterized in that the first gear ( 15) and the second (33) are straight helical-toothed wheels, in particular with involute toothing, in that the second axis of rotation is parallel to the first axis of rotation (27) and in that the second gear ( 33) has a maximum of seven,   in particular at most three teeth (47).   Positioning servo-drive according to claim 1, characterized in that the toothing of the second gear (33) is formed in one piece on a shaft (35) connected on one side with the electric motor (3), which shaft is axially mounted on both sides of the first gear wheel (15), on the gear case (1), in bearings (49, 51) of which at least the bearing (51) axially remote from the electric motor rests on a bearing surface (65) of the shaft (35) axially covering the toothing, at least partially.   3 positioning servo-drive according to claim 2, characterized in that the two bearings (49,51) rest on bearings of the shaft   (35), axially covering the toothing of the shaft (35).   4 positioning servo drive according to   any of claims 2 or 3, characterized in that   the bearing (51), remote from the electric motor (3), rests on a bearing surface (65) whose diameter is smaller than the diameter of the head circle of the second wheel toothed (33).   5 positioning servo drive according to   any of claims 2 to 4, characterized in that   the bearing (49) close to the electric motor (3) rests on a sleeve (67), in particular fixedly surrounding the shaft (35), the sleeve whose inside diameter is greater than the diameter of the outer circle of the second gear wheel (33).   6 positioning servo drive according to   any of claims 2 to 5, characterized in that   that the second gear wheel (33) is made of a single   part with the motor shaft (35) of the electric motor (3).   7 positioning servo drive according to   any of claims 1 to 6, characterized in that   the second gear wheel (33) is mounted on both sides of the first gear wheel (15) and in the vicinity thereof in bearings (49, 51) having centering surfaces (55, 59) associated with the first support base (21) is formed jointly on the first support base (21), on the same side of the first support base (21), in particular on the opposite side of the second base of support (25).   8 positioning servomotor according to claim 7, characterized in that the electric motor (3) is also fixed on the first support base (21) and the second gear wheel (33) is made of a   single piece with the motor shaft (35).   9 positioning servo-drive according to claim 8, characterized in that the drive shaft (35) is mounted on one side of the first gear (15), in a first bearing (51) axially free and on the other side of the first toothed wheel (15), in two other bearings (49, 61), one of which is an axially free bearing (61) and the other, in particular the bearing adjacent to the first toothed wheel (15), is a bearing (49) axially fixed. Positioning servo drive according to claim 9, characterized in that the further bearings (49, 61) are in a housing (53) of the electric motor (3) which is fixed to the first support base (21), on the same axis as a support seat (55) provided in the first support base (21), of the first bearing (51).   11 Servo-positioning drive according to   any of claims 7 to 10, characterized in that   a stop (73), placed in the path of rotation of the first gear (15) and limiting the rotation thereof in an end position, is mounted   removable on the first support base (21).   12 positioning servo-drive according to claim 11, characterized in that the stop (73) is a finger (73) extending between the first and second support bases (21, 25), parallel to the first rotation axis (27).   13 positioning servo-drive according to   any of claims 1 to 12, characterized in that   the first toothed wheel (15) has a serration of steel or bronze and the second toothed wheel (33) has a toothing made of steel and the toothed wheels (15, 33) rotate in a grease filling of the housing gearing (1).   14 positioning servo drive according to   any of claims 1 to 13, characterized in that   at the first toothed wheel (15) there are associated stop means (91; 95; 97; 105) which lock it in at least one of its end positions, in particular the end position. clutch totally the friction clutch.   Positioning servo drive according to claim 15, characterized in that the arresting means comprise a spring (91) stretched between the gear case (1) and the first gear (15), forcing the first gear wheel (15) in the end position in a position beyond the neutral position,   opposite to the other end position.   16 Servo positioning drive according to   any one of claims 14 or 15, characterized   in that the arresting means comprise a spring-arresting device (95), hooking the first gear (15) in its end position relative to to the gear case (1).   17 Positioning servo drive according to   any of claims 14 to 17, characterized in that   the stop means comprise a locking device (97) controlled, blocking the first toothed wheel (15) in its end position with respect to the gear case (1).   18 positioning servo-drive according to claim 17, characterized in that the locking device (97) comprises a locking lock (101) to   electromagnetic or hydraulic actuation.   19 positioning servo-drive according to claim 17, characterized in that the device   blocking comprises, at the outlet of the emitter cylinder (9), a blocking valve (105) controlled.