This invention relates to transmission devices for ground vehicles and more particularly for motor-cars.
The invention more specifically relates to transmission devices capable of automation and/or capable of providing numerous transmission ratios with a relatively simple structure.
Almost all the automatic transmission devices make use of differential mechanisms and more particularly epicyclic trains in which selective coupling means such as brakes, clutches and/or one-way clutches allow to change the transmission ratio provided by each elementary train. Conventionally, an epicyclic train provides one or the other of two ratios, one of the ratios being a direct drive obtained by means of a clutch which binds together two intermeshed rotary elements of the train. Epicyclic trains providing more than two ratios are known but they generally consist of so-called “complex” epicyclic trains, that is to say epicyclic trains having more than three intermeshed rotary elements and which are in fact equivalent to at least two elementary epicyclic trains.
As a result of the current demand for automatic transmissions offering a great number of different transmission ratios, e.g. five or even six, it becomes usual to design automatic transmissions comprising four or even five epicyclic trains. Such transmission devices are heavy, expensive, cumbersome, and poorly efficient in terms of energetic efficiency.
Furthermore, the numerous epicyclic trains result in a particularly complicated and expensive automatic control.
EP-A-0 683 877 discloses automatic transmission devices in which the automatic control is made simpler thanks to exploitation of the axial thrust of helical teeth, at the same time as a measurement of the transmitted torque and as an actuating force which is proportional to this torque. This force maintains in the disengaged condition a direct-drive clutch mounted between the input element and the output element of the epicyclic train when the epicyclic train operates as a speed reducing gear. Simultaneously, the third element of the train is maintained stationary by a one-way clutch (free-wheel) when the engine torque is motive and by an auxiliary brake subjected to an hydraulic actuation when the engine torque is reversed (engine-brake operation). The engagement of the direct-drive clutch takes place under the effect of centrifugal fly-weights when the rotational speed is high enough for allowing such fly-weights to overcome the axial tooth thrust. The hydraulic actuating force is also used for influencing the automatic behaviour of the transmission, that is to say for altering the “natural” balance between the tooth thrust and the centrifugal actuating force.
With this known device, the control is admittedly less complicated and energy-wasting but again a simple epicyclic train provide only two ratios. Furthermore, numerous thrust bearings are necessary, which are a cause of noise and wear.
The axial displacements need splines operating under load, which have a tendency to “pollute” the torque and speed signals provided by the tooth thrust and by the centrifugal fly-weights respectively.
The change-over of the known epicyclic train between one and the other of its two transmission ratios concerns all the components of the train and needs a relatively complicated synchronisation between actuating members. Although an epicyclic train is theoretically able to provide relatively numerous transmission ratios, it has not been practically possible to provide more than two, taking into account the complicated shifting process from one to the other of the two ratios.
An object of this invention is to provide a transmission device wherein the means necessary for shifting from one ratio to the other in a differential mechanism are remarkably simplified.
Another object of this invention is to provide a transmission device in which a simple differential mechanism, that is to say with only three intermeshed elements, is capable of providing more than two transmission ratios.
A further object of the present invention is to provide a transmission device allowing to provide numerous ratios with a remarkably simple structure and an enhanced mechanical efficiency.
According to a first aspect of the invention, a transmission device wherein a differential mechanism comprises:
With this device, the first rotary element of the differential mechanism is involved in all the coupling changes which are necessary for changing the transmission ratio. The first rotary element is
The other elements constituting the transmission device are thus rendered much more simpler. The friction coupling means can be spatially grouped close to each other in a particularly advantageous manner. The actuating means are simpler because each friction coupling means has a part which is fast with the first rotary element and it is therefore no longer necessary to transmit forces between elements rotating at different speeds. The inverter control means, which is typically connected for common rotation with the first rotary element may, between its two stable conditions, move through a floating position where the two friction coupling means are both disengaged. This is not a drawback because the one-way clutch simultaneously realises the situation corresponding to engagement of the first selective coupling means. To this end, the one-way clutch is mounted in parallel with the coupling means which is engaged for the operation providing the lower of the two transmission ratios, and the direction forbidden by the one-way clutch is that which would produce a still lower transmission ratio.
It is particularly advantageous to cause the first rotary element of the differential mechanism to be integral with the inverter control means and to contribute to actuation of the inverter control means by way of the tooth thrust, the teeth being made helical.
In this manner, the structure is simple and reliable and the tooth thrust is transmitted to the inverter control means without alteration. The inverter control means is preferably implemented as a simple pressure member having two opposed faces each of which is capable of tightening a respective one of the first and second friction coupling means.
As a rule, one-way clutches available in the commerce do not allow relative axial displacement. To enable the first rotary element to move axially despite provision of the one-way clutch between said first and second element, there is a preferably provided mechanically in series with the one-way clutch between the first rotary element and the second element, a means for common rotation and axial displaceability.
This coupling for common rotation is preferably mounted operatively between one of the first and second elements and a one-way clutch support. There is provided mechanically in parallel with the one-way clutch, an axially unslidable bearing between the one-way clutch support and the other of said first and second elements. Thus, the one-way clutch is perfectly protected from any axial stress.
On the other hand, for avoiding abnormal friction in the means for common rotation with axial slidability, it is preferred that the first rotary element is guided for axial sliding independently of the means for common rotation with axial displaceability.
The means for common rotation may be mounted between the first element and the one-way clutch support. The support therefore rotates at the same speed as the first rotary element while being made axially fast with the second element which is typically the casing element. The support is then adapted to bear another actuating means, such as a spring, which can thus axially urge the first rotary element without any need of interposing any axial thrust bearing.
A still further actuating means can consist of an hydraulic pushing element which is attached to the first rotary element, is coaxial therewith and can simultaneously contribute to the slidable guiding of the first rotary element. Consequently, all the actuations which are necessary for the ratio-changes may be performed solely by displacement of the first rotary element and of the inverter control means which is attached thereto, under multiple control forces and without transmission of the control forces through axial thrust bearings.
For selection between two transmission ratios in an epicyclic train, there has just been described an elementary structure for coupling and control which is essentially grouped together onto one of the rotary elements of the differential mechanism. The invention also encompasses provision of another such elementary structure onto another one of the rotary elements of the differential mechanism. The third rotary element of the differential mechanism may for example be permanently connected to one of the input and output rotary connection elements, e.g. the output element. There is thus provided an epicyclic train capable of four different operating conditions.
If a same rotary connection element, e.g. the input element, is managed to be associated with the two friction coupling means which are not in parallel with a one-way clutch, one of the four operating conditions corresponding to the case where the above-mentioned two friction coupling means are disengaged is a neutral condition which is useful e.g. for allowing the vehicle to remain stationary while the engine shaft of the vehicle rotates. If the two other selective coupling means are brakes blocking the differential mechanism and, therewith, the output connection element, a parking brake function is simultaneously fulfilled. For shifting from this neutral condition to one of the three other conditions corresponding to a transmission ratio, it is merely necessary to change condition of one of both inverter control means and this can be made with a progressivity which is high enough to ensure progressive starting of the vehicle. There is thus provided with a sole simple epicyclic train a transmission device offering at the same time three transmission ratios, one neutral condition and a progressive starting device capable of allowing to dispense with the clutch or torque converter which is conventionally provided between the engine and the transmission device in a motor car.
According to another aspect of the invention, it is possible to use in the transmission device two differential mechanisms which are controlled in the just described manner. One of the conditions of one of the differential mechanisms may be a reverse run ratio. Preferably, the reverse run ratio is provided in the differential mechanism which is located further downstream.
Even with a single simple differential mechanism, it is possible, as will be seen, to provide a several-ratios forward drive and a reverse drive.
According to a further aspect of this invention, there is provided a transmission device wherein a transmission mechanism comprises
This aspect of the invention provides a possibility of dispensing with the conventional input clutch or input torque converter. A friction coupling means provided in the transmission mechanism is operable for providing a neutral condition in which the power transmission flow path from the prime mover to the load to be driven e.g. the wheels of a vehicle, is interrupted within the transmission mechanism.
Furthermore, the axial tooth thrust created by the gear teeth in the transmission is used as an actuating force for the friction coupling means. If the tooth thrust is in a direction corresponding to engagement of the friction coupling means, the result is a reduction of the additional force which is necessary for engaging the friction coupling means. Typically, this additional force is produced by the controllable actuator, such as a hydraulic actuator. Disengagement of the clutch can be performed by a spring which is strong enough to counteract the tooth pressure when the controllable actuator is de-energized. Such a device is able to perform progressive start of the vehicle when the transmission device is initially in the neutral condition while the vehicle engine has being previously started. The controllable actuator is controllably energized for performing progressive, smooth start of the vehicle. A regulation can be provided for avoiding any shocks. For example, the acceleration of the vehicle may be detected, and compared to a desired value. The result of this comparison is the basis of an adjustment of the level of energization of the controllable actuator and/or of the power and/or r.p.m. of the engine.
It is also possible to arrange the transmission mechanism so that the direction of the tooth thrust is contrary to the direction of the force produced by the controllable actuator. The starting function is then to some extent self-regulated because an excessively high acceleration of the vehicle produces an increase of the tooth pressure, this increase tending in turn to somewhat disengage the clutch, i.e. reduce the grip in the clutch. The drawback of this solution is that the force to be produced by the actuator for engaging the friction coupling means is high because it has to overcome the tooth thrust and furthermore to engage the clutch.
According to a still further aspect of this invention, there is provided transmission device wherein a transmission mechanism comprises
The two friction coupling means allow to select one or the other of two transmission ratios. When the two friction coupling means are both disengaged, a neutral condition is realized in the transmission mechanism, allowing the engine of the vehicle to rotate without any corresponding rotation of the drive wheels of the vehicle. A remarkably simple structure is provided for selecting between three operating conditions.
Preferably, a fourth condition is available, with the two friction coupling means being both engaged. Such a fourth condition is in most cases a direct drive condition.
According to a still further aspect of the invention, there is provided a transmission device wherein a differential mechanism comprises:
A remarkably simple structure is provided for a three speed transmission mechanism with a number of toothed wheels which may be as low as three.
With almost no supplemental complexity a neutral condition is furthermore provided when both modules disconnect the input connection element from the sun wheel and from the crown wheel respectively.
According to a still further aspect of this invention, there is provided a transmission device comprising:
Such a six-speed mechanism with the described ratio-gaps distribution may be of the type defined in the preceding aspect of the invention.
Other features and advantages of the invention will appear from the following description, relating to non limiting examples.
In the attached drawings:
In the example shown in
Would the transmission device be limited to what has just been described, it would operate only as a speed-reducing gear and only if the torque applied onto the input shaft 31 is a motive torque. In such a case, the load undergone by the planet carrier 7 from the output shaft 41 tends to stop the spindles 71 so that the motive torque applied onto the crown-wheel 6 tends to cause reverse rotation of the sun-wheel element 5. But this is prevented by the one-way clutch 8, so that the sun-wheel element 5 is stopped and the planet carrier 7 rotates at a speed which is intermediate between the zero speed of the sun-wheel element 5 and the speed of the crown-wheel 6 corresponding to that of the input shaft 31.
If the torque applied to the engine shaft 31 is negative, i.e. when the engine of the vehicle operates has a brake, the wheels of the vehicle tend, through the output shaft 4, to cause the planet carrier 7 to rotate faster than the crown-wheel 6 connected to the input shaft 31 and this tends to cause rotation of the sun-wheel 5 still faster than the planet carrier 7, an occurrence which is not prevented by the one-way clutch 8. This faulty operation must be avoided and would result in the engine coming back to idle without braking the vehicle. Therefore, there is provided between the sun-wheel element 5 and the casing element 2 a first friction coupling means—or brake 9—which is mechanically in parallel with the one-way clutch 8. When engaged, the brake 9 makes the sun-wheel 5 stationary with respect to the casing element 2 and thus allows the transmission device to operate as a speed-reducing gear when the torque applied to the input shaft 31 is negative, in the same manner as when the torque is positive. The brake 9 may be dimensioned in a manner which is just enough for the braking operation, which involves much weaker torques than the peak motive torque.
The transmission device furthermore allows to realize a direct drive ratio thanks to a second friction coupling means—or clutch—10 capable of selectively coupling for common rotation two of the three rotary elements 5, 6, 7 of the epicyclic train so that the whole epicyclic train rotates as a sole part about the axis X. This is automatically permitted by the free wheel 8 but needs to disengage the brake 9.
According to an important feature of this invention, the second friction coupling means 10 is associated to the same rotary element, i.e. in the represented example to the sun-wheel element 5, as the other already described coupling meams, i.e. the one-way clutch 8 and the first coupling means 9.
More particularly, in the represented example, the second friction coupling means is mounted operatively between the sun-wheel element 5 and the input connection means 3.
It has been explained hereinabove that engagement of the second friction coupling means 10 needs to disengage the first friction coupling means 9. Conversely, engagement of the brake 9 needs to disengage clutch 10. To this end, according to a further important feature of the invention, a single control member 111 operates as an inverter between two stable conditions in each of which a respective one of the friction coupling means 9, 10 is engaged and the other, respectively, is disengaged. In the illustrated examples, inverter control means 111 is an axially movable pressure member. When urged towards the right of
Pressure member 111 is integral with the sun-wheel element 5 and therefore rotates at the same speed of rotation as the latter. Since both friction coupling means 9 and 10 both have the function of selectively connecting the sun-wheel element 5 with a respective other element of the mechanism 1, the integral connection of pressure member 111 with sun-wheel element 5 allows to realize pressure member 111 in the form of a common pressure member having two opposed pressing faces, i.e. a pressing face 112 for the stack of discs of brake 9 and a pressing face 113 for the stack of discs of clutch 10.
Generally speaking, the one-way clutches available in the commerce need to be mounted between two components which are axially stationary with respect to each other. Thus, taking into account the axial movability of sun-wheel element 5, the one-way clutch 8 cannot be directly mounted between the sun-wheel element 5 and the casing element 2. For this reason, there is provided a support 51 having on its outer periphery axial splines 52 engaging corresponding axial splines 53 of the sun-wheel element 5, whereby sun-wheel element 5 is slidable with respect to the support 51 while being coupled for common rotation therewith. The support 51 is made axially stationary with respect to the casing element 2 by means of an axially unslidable bearing 54 mounted between the support 51 and the stator shaft 21. The one-way clutch 8 is also mounted between support 51 and stator shaft 21 in parallel with bearing 54.
For the inverting control of both friction coupling means 9 and 10, the inverter control means 111 is subjected to the coordinated action of three actuating means:
Assuming that the tooth thrust is oriented towards the right (arrow F1) when the torque is motive, the operation is as follows:
During engine brake operation, the tooth thrust is reversed while taking a relatively low value which is not enough for overcoming the springs force 114. The device thus normally operates as a speed reducing gear except if an appropriate hydraulic pressure is applied within the chamber 22. During transition between both operating conditions, i.e. between both stable conditions of the control member 111, there is an intermediate condition where none of both friction coupling means is engaged. Assuming that the torque applied to the input shaft 31 is motive, the simultaneous disengagement of both coupling means 9 and 10 is not a problem since the sun-wheel element 5 remains stuck by the one-way clutch 8 so that the operation takes place in the speed-reducing mode. If by contrast the torque applied to the input shaft 31 is negative, there is a theoretical risk that the speed of rotation of the sun wheel element 5 increases, and that the speed of the input shaft 31 decreases while the output shaft 41 would accelerate. But practically this effect is small taking account of the inertia of the load applied to shaft 41 (the mass of the vehicle), of the low value of the negative torque applied to the shaft 31, and of the short duration of this situation.
It is also possible to chose the angle of helix of the teeth so that the tooth thrust occurs in the direction F2 when the torque applied to the input shaft 31 is motive. In such a case, the spring 114 have to be powerful enough for maintaining the device in the speed reducing operation in all the situations where this may be practically desirable against the tooth thrust F2. To this end, it is not necessary that the springs provide a great excess of force, it is enough that the clutch 10 be released even if brake 9 is only weakly engaged, since the one-way clutch 8 performs the function of maintaining sun-wheel element 5 stationary. During the engine brake operation, brake 9 is more tightly engaged since the tooth thrust is reversed and adopts direction F1.
For the direct drive operation, the chamber 22 is fed with a pressure which is high enough for engaging clutch 10 strongly enough.
As shown in phantom lines in
Shifting to the direct drive operation occurs when the tooth thrust F1 sufficiently decreases and/or when a pressure or a supplemental pressure sufficiently high is applied within the chamber of actuator 116. The engine brake operation necessarily occurs in direct drive because all the actuating forces are then directed towards the left of
Still other combinations are possible, e.g. by causing the actuator to operate in a direction contrary to the springs 118. In such a case, the springs 118 tend to promote direct drive operation and the actuator may be energized for promoting engine brake operation. It is then advantageous to chose the direction F1 for the tooth thrust when the torque applied to the input shaft 31 is motive. For the engine brake operation, the tooth thrust is reversed and promote direct drive operation but this can be selectively counteracted by an appropriate hydraulic pressure.
The example of
In this embodiment, in addition to the sun-wheel element 5 which may be selectively connected with the input connection element 3 or with the casing element 2, the crown-wheel 6 can be selectively connected with the input connection element 3 and with the casing element 2, another portion 23 of which is now illustrated. The grouped control and coupling structure for the crown-wheel 6 is very similar to that described for sun-wheel element 5. More specifically, an inverter control member 211 is integral with crown-wheel 6 and axially displaceable therewith. Member 211 comprises a pressing face 212 for selectively engaging brake 209 operatively mounted between the crown-wheel 6 and the portion 23 of the casing, and an opposed pressing face 213 for selectively engaging clutch 210 mounted operatively between the crown-wheel 6 and the input connection element 3. The portion 23 of the casing element 2 defines a chamber 24 of an hydraulic actuator 216, with a piston 217 being fast with the crown-wheel 6 and slidable within said chamber. A support 251 is coupled for common rotation with but axially slidable relatively to the crown-wheel 6 thanks to splines 252, 253. Between the support 251 and the casing element portion 23, there is provided an axially unslidable bearing 254 in parallel with a one-way clutch 208 forbidding rotation of the crown-wheel 6 with respect to the casing element 2 in a direction contrary to the normal direction of rotation of the input shaft 31. Springs 214 mounted axially between the support 251 and the piston 217 axially urge the crown wheel 6 in a direction contrary to that of the hydraulic pressure which may prevail in chamber 24.
The transmission device according to
The sun-wheel element 5 having helical teeth, the crown-wheel 6 also has helical teeth and consequently, the grouped control and coupling structure associated with the crown-wheel 6 is also subjected to the coordinated action of three forces comprising a tooth thrust, a resilient force and a force which is selectively applied by hydraulic means.
Again, different combinations of directions of these three forces are possible as explained with reference to
It is noticeable that despite provision of four operating conditions in a single simple epicyclic train, no control and no coupling concerns e.g. the planet carrier 7 and the output shaft 41, and no thrust bearing is necessary for transmitting thrust between rotary members having different speed.
As in the example of
An appropriate choice for the direction of the actuating forces, more specifically among the four possible combinations described as to the example of the grouped structure of
During transition between the first and the second reduction ratio of
In the neutral condition, springs 114 and 214 maintain brakes 9 and 209 in the engaged condition so that the whole epicyclic train and therewith the output shaft 41 are immobilised against rotation, whereby a parking brake is obtained. In this situation, it is possible to cause movement of the input shaft 31, for example by starting the vehicle engine, and then to progressively start the vehicle by progressively applying an hydraulic pressure within chamber 22 for progressively engaging clutch 10 and introducing a progressive start of the vehicle. Consequently, the transmission device of
The transmission device of
In the example of
Mechanism 301 distinguishes over that of
The various components of the mechanism 301 may be recognised from their references which are identical to those of
Mechanism 302 comprises a simple epicyclic train essentially comprised of a sun-wheel element 350, a crown element 360 and a planet-carrier 370. Crown 360 is integral with output element 4 and is made axially stationary by means of bearings 365 with respect to a sleeve 26 belonging to the casing element 2. The output element 4 comprises gear teeth 42 arranged coaxially with the main axis X. The gear teeth 42 are intended to mesh with a pinion, not shown, supported along an axis which is parallel to axis X. The planet-carrier element 370 carries eccentrated spindles 371 on which planets 372 are rotatably mounted, which mesh with the teeth of the sun-wheel element 350 and with the teeth of the crown-wheel element 360.
The sun-wheel element 350 is associated with a grouped coupling and control structure comprising brake 309 for selectively connecting the sun-wheel element 350 with the casing element 2, a clutch 310 for selectively connecting the sun-wheel element 350 with the input connection element 330, an inverter control member 311 comprised of a pressure member which is integral with the sun-wheel element 350 and comprises a pressing face 312 for engaging the brake 309 in one of its two stable conditions and an oppositely directed pressing face 313 for engaging clutch 310 in the other of its two stable conditions. The sun-wheel element 350 defines with the casing 2 a chamber 322 of an hydraulic actuator 316 disposed for urging sun-wheel element 350 towards the stable condition corresponding to engagement of clutch 310 and disengagement of brake 309 when fed.
According to a difference over the grouped structure associated with the sun-wheel element 5 of mechanism 301 the one-way clutch 308 is mounted in parallel with clutch 310 and no longer in parallel with brake 309. One-way clutch 308 prevents sun-wheel element 350 from rotating faster than the input connection element 330. However, the mounting fashion itself of the one-way clutch is similar to that already described: the one-way clutch 308 is mounted in parallel with an axially unslidable bearing 354 between the input connection element 330 and the support 351. The input connection element itself is axially immobilized with respect to the casing element 2 by a bearing diagrammatically illustrated as 333. The support 351 is coupled for common rotation with the sun wheel element 350 by means of splines 352, 353. Springs 314 are mounted between the support 351 and the sun wheel element 350 for urging the sun-wheel element 350 in a direction opposed to that defined by the pressure in the hydraulic chamber 322. The teeth of the epicyclic train are helical and consequently, as in all the grouped structures described hereinabove, sun-wheel element 350 is subjected to a combination of three forces comprising the tooth thrust, the resilient force of the springs 314 and the hydraulic pressing force in the chamber 322.
The mechanism 302 furthermore comprises a dog-clutch system 373 comprising a control member 374 carrying coupling teeth 376. The control member 374 is movable between the neutral position “N” which is illustrated, a forward drive position “D” in which the planet carrier 370 is coupled for common rotation with the input connection element 330 of the second mechanism 302, and a reverse drive position “R” in which the planet carrier 370 is discoupled from the input connection element 330 and coupled with the sleeve 26 integral with the casing element. The control member 374 is a tube which is movably inserted between the stator shaft 21 and the stator sleeve 26.
Operation of the second mechanism 302 will now be described when the dog clutch is in the “D” position allowing two different forward drive ratios.
When the clutch 310 is engaged, the input connection element 330 is connected for common rotation at the same time with the sun wheel element 350 by the clutch 310 and with the planet carrier 370 by the coupling teeth 376 of the dog clutch 373. The mechanism 302 thus operates in a direct drive mode. When the clutch 310 is released, and the brake 309 engaged, the sun-wheel element 350 is blocked with the casing element 2 and the input connection element 330 solely drives the planet-carrier 370. Consequently, the planets 372 roll about the teeth of the sun-wheel 350 and cause the crown-wheel 360 to rotate faster than the planet-carrier 370. The mechanism 302 then operates in an overdrive mode.
During transition between these two stable conditions, the crown 360 tends to be retarded by the load applied to the output element 4 and consequently the sun-wheel element 350 tends to rotate faster than the assembly comprised of the planet carrier 370 and the input connection element 330. But this is prevented by the one-way clutch 308.
When the dog clutch device 373 is in the “R” position, the planet carrier 370 is prevented from rotation and consequently the planets 372 operate as movement reversal means between the sun-wheel 350 and the crown wheel 360. In this case, clutch 310 must be engaged by an appropriate hydraulic pressure within chamber 322 against the springs 314 so that the motion introduced by input connection element 330 be transmitted by the sun-wheel element 350. The movement reversal occurs with a speed reduction since the diameter of the crown 360 is greater than that of the teeth of the sun-wheel element 350.
By an appropriate choice of the ratios between the different diameters of the toothed elements, a choice of which
These six ratios are the following:
Position, “N” of the dog clutch 373 results in releasing the output element 4, a condition which may be useful, e.g. for pushing the vehicle by hand or towing it despite the fact that in the absence of energisation of the mechanism 301, a parking brake condition is realised in mechanism 301. This possibility of neutralizing the parking brake function results from mechanism 301 being located upstream of the dog-clutch system with respect to the power flow path between the engine and the wheels of the vehicle.
The transmission device of
The way in which the three ratios of the first mechanism 301 are obtained in a basic epicyclic train, generates a much greater ratio-gap between the first and the second ratio than between the second and the direct drive ratio. More specifically, the first ratio-gap is substantially equal to more than the square of the second gap, and still more typically about a cubic of the second ratio gap. For example, the ratios are 1:4.2, 1:1.4 and 1:1, giving a first ratio gap of 4.2/1.4=3.00 between the first and the second ratio, and a second ratio gap of 1.4/1=1.4 between the second and the direct drive ratio. The overdrive ratio in the second mechanism is selected so as to be intermediate between the first and of the second ratio gaps in the first mechanism, i.e. about 1.8, thus with the overdrive ratio being about 1:1.8.
The example of
The bi-axial arrangement of
The example of
The planet carrier 7 is no longer rigidly connected to the output shaft 41. There is introduced in the mechanism a dog-clutch device 73 comprising
In forward drive, the operation is the same as in
There is thus realised with a single simple epicyclic train the entirety of an automatic transmission for a vehicle with three forward drive ratios, a reverse drive, a neutral, and a progressive starting device. For shifting from forward drive to reverse drive a dog-clutch system is normally satisfactory since such a shift normally takes place when the vehicle is stopped, a situation in which all the parts involved in the dog-clutch shift are stationary even if the engine rotates the input shaft 31.
In the reverse drive mode, the crown wheel 6 is rotating while the support 251 is stationary. Therefore, an axial thrust bearing 141 has been inserted between the spring 214 and the crown wheel element 6.
The embodiment of
The springs 114 and 214 have been suppressed and replaced by a single spring means 14 inserted between the sun wheel 5 and the crown wheel 6 for urging them in mutually contrary directions which are, for each of them, the same as those promoted by springs 114 and 214 in
In each of the first and second ratios of the embodiment of
In direct drive operation, both hydraulic actuators are energized to compress the spring means 14 to a maximum while engaging, as in the embodiment of
In a modified embodiment, not shown, the spring 14 and thrust bearing 142 assembly may be replaced by a supplemental hydraulic actuator which is de-energized for the direct drive operation.
The embodiment of
The embodiment of
The first mechanism 301 is generally similar to that of
The output connection element 4 of the first mechanism 301 is provided with gear teeth meshing with gear teeth of an intermediate output element 45 on which the output teeth 42 are integrally formed and which is rotatably mounted onto the input shaft 131 of the transmission device. Thus, the input (shaft 131) and the output (teeth 42) of the whole transmission device are coaxial. This is of advantage because it allows to freely orient the transmission device about the common axis X3 of the input and the output in the motor compartment of a vehicle, depending on the available space.
The reverse drive mechanism 303 is mounted about geometrical axis X3 so as to selectively by-pass the first mechanism 301. The reverse drive mechanism 303 comprises a dog clutch system 361 which selectively connects for common rotation the crown-wheel 360 of the second mechanism and its integral output connection element 304 with a pinion 82 which is freely rotatable about input shaft 131. Pinion 82 meshes with an intermediate eccentrated stepped pinion 83 which in turn meshes with a third tooth set 84 of the intermediate output member 45.
The arrangement is such that in direct drive, the direction of movement of the output teeth 42 is contrary to that of input shaft 131 by virtue of intermediate pinion 81 between the output connection element 304 of the second mechanism 302 and the input connection element 3 of first mechanism 301, whereas the output teeth 42 and the input shaft 131 have the same direction of rotation in the reverse drive mode. The dog clutch 362 of the dog clutch system 361 is movable between a “N,D” position, shown in
The embodiment of
The second mechanism 302 is similar to that of
The first mechanism 301 is identical to that of
Furthermore, instead of selectively connecting the crown wheel 6 with the casing element 2, the clutch 209 and one-way clutch 208 assembly connects the crown-wheel 6 with a cage 86 which is rotatable about the axis X4 of the first transmission mechanism 301.
The output element 4 and the cage 86 are provided with respective gear teeth which mesh with corresponding teeth which are integral with respective rings 87, 88, which are rotatable about input shaft 131 and coaxially therewith. A stationary ring 89 is integral with casing element 2 and is axially aligned with rings 87 and 88 and mounted between them. The three rings 87, 88 and 89 are rotatable about a tubular shaft of intermediate connection element 45 and between two toothed flanges 46 of this tubular shaft. A first dog-clutch 91 selectively couples for common rotation ring 87 with the output teeth 42 of the transmission device for direct drive, or with the stationary ring 89 so as to immobilize the planet carrier 7 for reverse drive. A second dog-clutch 92 selectively connects for common rotation the second ring 88 with the output teeth 42 or with the stationary ring 89 so as to either connect the cage 86 with the output teeth for the reverse drive or to the casing 2 for the direct drive. Both dog clutches 91, 92 are synchronized by a coupling member 93.
The embodiment of
The second differential mechanism 302 is replaced with a two-speed layshaft mechanism 402 which simultaneously performs transfer of the power from axis X3 along which input shaft 131 extends, onto parallel axis X4 of the first differential mechanism 301, not shown, and more particularly from input shaft 131 of the transmission device to input connection member 3 of the first differential mechanism 301.
Mechanism 402 comprises two impeller pinions 410, 420, of different diameters, which are rotatably mounted onto input shaft 131, and mesh with respective receiver pinions 411, 421 which are integral with input connection element 3. The smaller one of the impeller pinions 410 is selectively coupled to input shaft 131 by a one-way clutch 408 mounted in parallel with a clutch 413 which is engaged when an actuator 416 is energized.
Impeller pinion 420 having the larger diameter is slidably mounted onto input shaft 131 and is selectively coupled for common rotation therewith when a friction clutch 423 is engaged. Engagement of clutch 423 is initiated by an hydraulic actuator 426 axially pushing impeller pinion 420 in the direction corresponding to the tooth thrust 425 experienced by impeller pinion 420 when transmitting a motive torque from input shaft 131 to input connection member 3. There is provided between impeller pinion 410 and 420 a spring means 414 in series with a thrust bearing 442.
The operation of the embodiment of
When none of the actuators 416 and 426 are energized and a motive torque is applied to input shaft 131, one-way clutch 408 drives impeller pinion 410, which in turn drives input connection element 3 with the lower of the two transmission ratios. The actuator 416 may be energized for maintaining the same transmission ratio in case the torque applied on input shaft 131 would become negative (engine-brake operation).
The mechanism 402 is shifted into its higher transmission ratio when actuator 416 is deenergized and actuator 426 is energized for engaging clutch 423. This results in a slower rotating speed of input shaft 131 while the rotating speed of impeller pinion 410, which is determined by the rotating speed of input connection element 3, remains unchanged, as allowed by one-way clutch—or free-wheel—408.
The embodiment of
The first mechanism 301 and the second mechanism 402 are mounted in series along a same geometrical axis X5. The vehicle engine 101 is connected to the input connection element 3 of the first mechanism 301 through an input clutch 102. The first mechanism 301 is essentially similar to that of
Instead of being rigidly connected to the input connection element 3, both receiver pinions 411 and 421 of the second mechanism 402 are rigidly connected to a ring 94 which is selectively connected to the output teeth 42 by a dog-clutch 96. Another dog-clutch 97 selectively-connects the output teeth 42 with an intermediate reverse drive member 98 which integrally includes a pinion 99. An intermediate pinion 181 meshes with pinion 99 and with gear teeth 182 provided on the input connection member 3 of the first mechanism-301.
The intermediate output member 98, the output teeth 42 and the ring 94 as well as the receiver pinions 411 and 421 extend along a common axis X6 which is parallel to axis X5 of the first and second mechanism 301, 402.
Dog-clutches 96 and 97 are urged apart from each other by a spring 183 whereby, in the rest position of both dog-clutches, the output teeth 42 are disconnected both from the forward drive motion arriving through either one of receiver pinions 411 or 421, and from the reverse drive motion arriving through the intermediate reverse drive connection member 98. Starting from this situation, the forward drive mode is established by pushing dog clutch 96 toward dog clutch 97 being maintained at rest, and conversely the reverse drive mode is established by pushing dog clutch 97 towards dog clutch 96 being maintained at rest.
In the reverse drive mode, both the first mechanism 301 and the second mechanism 302 are by-passed.
The input clutch 102 is therefore necessary for allowing progressive start of the vehicle in reverse drive.
The example of
The reverse drive connection 182, 181, 99, 98, 97 between the input of the first mechanism and the output teeth 42 is completely suppressed and the output teeth 42 are rigidly connected to the receiver pinions 411 and 421 as well as to a reverse receiver pinion 484. An intermediate pinion 483 meshes with the reverse receiver pinion 484 and with a reverse impeller pinion 482 mounted for free rotation about the tubular shaft 41 in the second mechanism 402.
Instead of being mounted between the impeller pinion 410 and the input connection element of the second mechanism, the one-way clutch 408 is now mounted between the impeller pinion 410 and a ring 184. A dog-clutch 186 selectively connects the tubular shaft 41 with the ring 184 for direct drive, or with the reverse impeller-pinion 482 for reverse drive. Since power flows through the first mechanism 301 both for forward drive and reverse drive, this embodiment does not need any input clutch 102 (
The embodiment of
The first mechanism 301 has been modified so that each friction coupling device 9, 10, 209, 210 is controlled by a specific actuator 317, 318, 319, 320, which are illustrated by mere arrows. The sun-wheel element 5 and the crown wheel element 6 are stationary in the axial direction. For this reason, it is no longer necessary to provide bearings in parallel with the one-way clutches 8, 208.
The spring means are eliminated.
In this embodiment, the available gear ratios are the same as in
The second mechanism 302 has not been modified over that of
Of course the invention is not limited to the shown and described embodiments.
Other actuating forces than those represented may be involved, e.g. forces produced by centrifugal flyweights promoting operation with a higher transmission ratio when the rotating speed increases, or else a second hydraulic force in a direction contrary to the first one for being able to influence positively in one or the other direction the operating condition of a grouped actuation and control structure.
It has been seen in the embodiment of
This invention is compatible with complex differential mechanisms, having at least four rotary elements. It is then possible to increase the number of grouped coupling and control structures.
Number | Date | Country | Kind |
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00 14839 | Nov 2000 | FR | national |
Number | Date | Country | |
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Parent | 10257527 | Oct 2002 | US |
Child | 11248850 | Oct 2005 | US |