WO1995013487A1

WO1995013487A1 - Electronically actuated and controlled power transmission system

Info

Publication number: WO1995013487A1
Application number: PCT/US1994/012926
Authority: WO
Inventors: Yves J. Kemper
Original assignee: Kemper Yves J
Priority date: 1993-11-12
Filing date: 1994-11-10
Publication date: 1995-05-18
Also published as: AU1174895A

Abstract

An electronically actuated and controlled power transmission system includes an electronically controlled inductor (278) which is used as a brake when its reaction member is rotatably locked by the action of pulley (224), inductor (278) moving axially diaphragm (232) relative to back plate (231) of the vehicle starting clutch (230) by varying the friction torque and/or the axial force applied on ball screw mechanism (233/236) by inductor (278) when pulley (224) prevents its rotation. Pulley (225) is driven rotatably by pulley (224) through the action of belt (226), and pulley (225) powers a mechanism transforming its rotation into an alternating axial movement of output rod (285) of gearbox actuator system (280), the alternating axial movement being utilized for the actuation of couplings or synchronizers. When the inductor (278) is electrically energized, rotation of the pulley (225) is prevented through the action of an electronically controlled magnetic friction brake system (223).

Description

ELECTRONICALLY ACTUATED AND CONTROLLED POWER TRANSMISSION SYSTEM

The present invention relates to power transmission systems of the type having a starting friction clutch and a multi-ratio multi-lay shaft gearbox actuated by one or more fork rods, and, more particularly, to such power transmission systems capable of electronic actuation and control.

Present foot-operated vehicular starting friction clutches, incorporating one or more discs, are all based on the same fundamental principles. They vary in the design detail, for example, in the type of spring used, such as helical or diaphragm springs, and in the way they are released, such as by pushing or by pulling a release thrust bearing. In the ensuing text, it is assumed that such a starting friction clutch assembly may be generalized as a type using a spring known in the art as a "diaphragm", and that the clutch is released by a control force transmitted to the diaphragm when it is controlled by a foot operated pedal. Also it is noted that the opening of a starting clutch, i.e., the complete interruption of the torque transmission between an engine and the gearbox, is obtained with a small fraction of the built in actual travel of the thrust release bearing. This large travel of the release thrust bearing is necessary to accommodate progressive wear of the starting clutch disc as well as variations in tolerances and play of parts between the foot operated pedal and the release bearing.

Manually operated multi-speed, multi-lay shaft, gearbox systems, are actuated by the movement of a hand operated shift lever. This shift lever is moved laterally to select one of the fork rods, and back and forth to engage alternately, two facing synchronizers controlled by a single fork rod, the middle position being called "Neutral". The gearbox is controlled either by a single shaft protruding from its housing, called a "gearbox control rod", by which rod rotation is used for fork rod selection, and axial rod movement is used for synchronizer actuation, or, by two separate gearbox control rods, one for fork rod selection, and the other for synchronizer actuation. It should be noted that the selection of a fork rod requires a relatively low force, as long as the two springs, presently used for bringing the hand operated shift lever to its middle position, are removed.

However, a relatively high axial force sometimes must be applied to engage the synchronizers in order to get an adequate, or fast synchronization, particularly when the gearbox is cold or when a shift takes place at high engine speeds.

A number of systems intended to automate manually operated power transmissions have been proposed to date. For those using hydraulic means including a hydraulic pump, a hydraulic reservoir and a pressure accumulator, the starting clutch as well as the fork rods are operated by hydraulic pistons controlled by electro valves. For those using electric means which may include electric motors and power screws for actuating the starting clutch, with possible the addition of an auxiliary counterbalancing spring in order to reduce power requirements of the motor, the axial and rotational movements of the gearbox control rod are obtained respectively by the action of two separate electric step motors, through the action of a linear movable and rotatable power screw.

All these systems are complex and therefore expensive to manufacture.

It is apparent therefore that there is a need for improvements, and particularly with the general acceptance of vehicle computer management systems, for power transmission systems which can be both electronically actuated and electronically controlled with low control power.

SUMMARY OF THE INVENTION It is the aim of the present invention to overcome the aforementioned problems and disadvantages, and to provide a simple and efficient electronically actuated and controlled power transmission of the type having a starting friction clutch incorporating a spring represented by a diaphragm and a multi-speed, multi-lay shaft, gearbox actuated by fork rods, in which the manufacturing costs are reduced and overall efficiency is increased relative to existing systems.

The advantages and purpose of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purpose of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a servomechanism for operating the starting clutch in an automotive drive train having an engine with a rotatable power output, the starting clutch having a rotatable starting clutch input including a backplate driven by the power output of the engine, and a rotatable starting clutch output, the starting clutch being adjustable by an actuating force between zero and maximum torque transmitting capacity, and having an axially biased movable control member for controlling the torque transmitting capacity. The servomechanism includes a torque to linear force conversion device coupled to the axially movable control member to adjust the actuating force of the starting clutch reversibly between zero and maximum. A rotatable friction device is normally retained in frictional torque transmitting engagement with the back plate by the axially biased movable control member, the rotatable friction device being connected to the torque to linear force conversion device to counter balance feed back torque converted from linear force of the axially biased moveable control member. An electromagnetic device is included to control the torque transmitting engagement of the friction device with the back plate in a manner to operate the torque to linear force conversion device to move the control member for actuating the starting clutch. In another aspect of the invention, the electromagnetic device comprises an inductor including a solenoid coil and a breech having a friction face, the inductor being supported so that the friction face is normally spaced from contact with the friction device. The inductor is operated to reduce torque between the rotatable friction device and the backplate and engage the friction face with the friction device to overcome the forces of the axially biased movable member and cause relative rotation between the backplate and the rotatable friction device in a direction to adjust the starting clutch toward zero torque transmitting capacity. The automotive drive train includes a multiple speed ratio gear box, a movable shifting member to shift the speed ratio of the gear box, and a rotatable drive element coupled to the breech to transmit engine power to the shifting member when the friction face of the breech is in engagement with the friction device and the starting clutch is adjusted to zero torque transmitting capacity. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Other advantages and further scope of the applicability of the present invention will become apparent from the detailed description to follow, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. In the drawings,

FIG. 1 is schematic half sectional view illustrating a preferred embodiment of the working components of the starting clutch actuator system of the invention; FIG. 2 is schematic sectional view illustrating a preferred embodiment of the working components of the starting clutch actuator system and the gearbox actuator system of the invention;

FIG. 3 is schematic enlarged partial half sectional view illustrating a preferred embodiment of the working components of the starting clutch actuator system illustrated in FIG. 2 of the drawings;

FIG. 4 is schematic enlarged sectional view illustrating a preferred embodiment of the working components of the gearbox actuator system illustrated in FIG. 2 of the drawings;

FIG. 5 is schematic sectional view illustrating an alternate embodiment of the working components of the starting clutch actuator system and the gearbox actuator system of the invention;

FIG. 6 is a schematic illustrating the electric components of the electronically actuated and controlled power transmission system of the invention;

FIG. 7 is a graph illustrating the relation between the gap and the magnetic axial force between the inductor and the disc of a typical Warner brake or clutch;

FIG. 8 is a graph illustrating the relation between the voltage applied to the solenoid and the magnetic axial force between the inductor and the disc of a typical Warner brake or clutch;

FIG. 9 is a graph illustrating the relation between the axial force applied to the inner edge of the diaphragm and the consequent axial travel of the inner edge for a conventional starting friction clutch;

FIG. 10 is a graph illustrating as an hypothetical example of how the voltage applied to the solenoid may vary as a function of time;

FIG. 11 is a partial cross-section illustrating another embodiment of the invention; and

FIG. 12 is a partial cross-section illustrating a variant of the embodiment shown in FIG. 1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings.

In the following detailed description, the reference numbers have three digits, the first digit referring to the figure number, the two others digits referring to the part number. Parts having the same purpose in the various drawings have in general the same last two digits.

Starting friction clutch systems are well known to one skilled in the art, and since this invention concerns the actuation and control of such clutches, the starting friction clutch system is not described herein in detail.

Multi-speed multi-lay shaft manually operated gearbox systems, actuated by one or two control rods protruding from the gearbox, are well known to one skilled in the art, and since this invention concerns the actuation and control of existing power transmission systems, the gearbox system is not illustrated in detail.

In FIG. 1 of the drawings, components of an embodiment 170 of the vehicle starting clutch actuator system of the invention are illustrated. The actuator system embodiment 170 is applied to a pull type starting friction clutch assembly 230, or "starting clutch", of which sectional view is illustrated in FIG. 2 of the drawings. FIG. 1 illustrates only components of the starting clutch assembly 230 illustrated in FIG. 2 of the drawings which interface directly with the clutch actuator embodiment 170 of the invention, i.e. the back plate 131/231, the diaphragm 132/232 and the housing 141/241. The actuator system 170 is intended to be operated electronically to control the opening and closing of starting clutches of a type commonly used for manual transmissions, particularly for vehicles. The actuator system 170 and the conventional starting clutch have a common axis of revolution 143/243. The actuator system 170 includes an electronically controlled friction brake system and a mechanism for transforming relative rotational movement into relative axial displacement. In the illustrated embodiment, as non limiting examples, ball ramp and ball screw systems 133/135/136 are used but other transforming systems known in the art might be used. The controllable brake system is preferably, but not necessarily of the type manufactured by Warner Electric, and includes a magnetic inductor 178, which can be brought into frictional engagement with a disc 134 under control. The inductor 178, as it is called in the art, comprises a solenoid 172, surrounded by a breech 171 and a body 173, both having a high magnetic permeability, these parts being fastened or otherwise secured together by adequate means in such a way that they cannot move relative to each other, either axially or rotatably, after their manufacture. One or more circumferential openings, known to one skilled in the art as "banana slots" 175, are machined on the friction surface of the breech 171 facing the disc 134, and such that the breech 171 tends to attract magnetically the disc 134 as soon as either an alternate or a direct electric current is supplied to the solenoid 172. The inductor 178 is fastened to a spring 174 by a series of rivets, or any other appropriate means. The spring 174, is preferably, but not necessarily, of the Belleville type, and assembled pre- stressed in such a way that the body 173 is biased axially against the gearbox housing 141 when the spring 174 is secured relative to the housing 141 by one or more bolts 142 or other appropriate means.

The disc 134 is in friction engagement with the pads 138 fastened by appropriate means to the back plate 131/132 of the starting clutch 230. In the embodiment illustrated in FIG. 1, the mechanism for moving the diaphragm 132 relative to the back plate 131 is of the ball ramp type. Ball ramps are well know in the art, and will not be discussed here in detail, other than to mention that they generally include two or three balls 135 rolling into variable depth or inclined tracks, machined respectively on the screw 133 and the bolt 136. The disc 134 is secured axially and rotatably to the screw 133 by adequate means, such as the illustrated spline and washer system.

As is well known in the art, the clutch diaphragm 132 is in the nature of a washer-shaped spring which acts to exert an axial bias in the central portion thereof. That bias urges the assembly of the bolt 136, the balls 135 and the screw 133 to the left, as shown in Fig. 1. Because the disk 134 is fixed axially to the screw 133, the disc 134 is normally held in torque transmitting frictional engagement with the pads 138 under the spring bias of the clutch diaphragm 132. When the screw 133 rotates relative to the bolt 136 in one rotational direction, the diaphragm 132 is moved against its spring bias toward the back plate 131 to open or disengage the starting clutch 230, whereas, when the screw 133 rotates in the opposite rotational direction, the diaphragm 132 moves away from the back plate 131 to close or engage the starting clutch. As it will be clear to one familiar with the art, the clutch actuator can be used as well with diaphragm starting friction clutches of the push type.

To describe the functioning of the vehicle starting clutch actuator system 170 of the described embodiment, it is assumed that the starting clutch is initially in the open position, and consequently that the diaphragm spring 132 has been pulled toward the back plate 131, pressure acting on the disc 237 of the starting clutch is zero, and therefore that the actual torque transmitting capacity of the starting clutch is zero. The lead of the screw 133 and the friction coefficient of the material of the friction pad 138 and the effective radius thereof are selected so that torque tending to rotate the screw 133, under the effect of an axial force applied by the diaphragm spring 132 on the bolt 136, is counterbalanced by the friction torque generated between the disc 134 and the friction pad 138 as well as the friction torque of the screw assembly. As a result, the screw 133 and the bolt 136 cannot rotate relative to each other under this axial force. However, as soon as an electric current is supplied to the solenoid 172 through the wires 151, the magnetic field created by the solenoid 172 tends to attract the disc 134 magnetically, but if the amount of electrical power supplied is such that the body 173 remains applied against the gearbox housing 141, because of the prestress of the spring 174, the disc 134 will continue to rotate with the back plate 131. It should be noted here that the torque r_ω precluding the rotation of the disc 134 relative to the back plate 131 is relatively high in comparison to the rotational inertia I of the screw 133, which means that the rotational acceleration ώ of the screw 133 is relatively high, the acceleration being given by the following expression:

ω = -ϋ

In order to be able to close the starting clutch 130 at a relatively slow rate, the solenoid 172 is supplied with a relatively high frequency alternating or pulsed current, such that the pressure between the disc 134 and the back plate 131 is reduced for relatively short intervals of time, at twice the pulsed current frequency f_elec. Consequently, the speed of rotation ft of the screw 133 relative to the back plate 131 is relatively slow, if the frequency is high since it can rotate only by a very little amount during each period. That speed ft can be controlled, either by varying the frequency f_θι_ec of the current supplied to the solenoid 172, or by supplying alternating electric current at a constant frequency -f_β2ec but for variable lengths of time.

When a sufficiently high level of direct current is supplied to the solenoid 172, the inductor 178 is pulled against the disc 134 and generates a friction torque between them. In this condition, the screw 133 is forced to rotate relative to the bolt 136. As a result, the diaphragm 132 is pulled toward the back plate 131, and the starting clutch 230 is opened. If the electric current is interrupted, relative rotation of the screw 133 and the bolt 136 is stopped and the pressure between the friction pad 138 and the disc 134 is increased. The starting clutch 230 therefore remains in the open position. The amount of release of the starting friction clutch 230 can be controlled by varying the amount of power supplied to the solenoid, since each level of power corresponds to a level of torque applied by the breech 171 on the disc 134, and therefore a level of axial force applied to the diaphragm spring 132. Since the actual torque capacity of the starting clutch 230 varies, in the range of utilization of the system 170, almost perfectly linearly with the force applied on the diaphragm 132 by the bolt 136, and since, each level of electrical power supplied to the solenoid 172 corresponds a level of force applied to the diaphragm 132, the torque capacity of starting clutch 230 varies with the amount of power supplied to the solenoid 172. This feature is particularly useful when it is necessary to maintain a certain speed differential between the engine 660 and the input of the gearbox 640, since the starting clutch must, in this case, be constantly released slightly or, further engaged by small amounts. It should be noted here that it takes a relatively low fraction of the axial movement of the bolt 136 to cancel the torque capacity of the starting clutch 230. The reason for this is that foot operated starting clutches 230 in production today are designed in such a way that part of the designed potentially available axial travel of the release thrust bearing is required not only for adjustments consequent to variations iri the tolerances and stack up, but most importantly, to compensate for the reduction in the thickness of its disc 237 over the time. However, in the clutch actuator system 170, when the starting clutch 230 is released with the pulsating current as described, the disc 134 maintains always a residual pressure on the friction pads 138, since it would take an infinite amount of time to release the pressure completely. Moreover, the pressure release is independent of the actual thickness of the disc 237, and its reduction over time. Therefore, whatever the wear of the disc 237, it always takes about the same travel to change the torque capacity of the starting clutch 230 from its maximum to zero. For the same reason, whatever the wear of the starting clutch 230, the relation between the torque capacity of the starting clutch 230 and the force applied by the bolt 136 to the diaphragm 132 stays relatively linear, allowing systems for detecting the reaction torque of the plate 174 as sensors of the actual interruption of engine power transmission.

A detailed description of an alternate method, according to the invention for controlling the starting clutch actuator 170 illustrated in FIG. 1 of the drawings, follows below.

To simplify the explanation, it is assumed i/ that the ball screw, or ball ramp, friction angle is negligible relative to its helix angle, ii/ that no coefficients of safety are included in the calculations, iii/ that the coefficient of friction between the disc 134 and the back plate 131, and as well as, that the coefficient of friction between the disc 134 and the inductor 178 are both constant, and iv/ that the effect of the torsional vibrations generated by the engine will be assume negligible. The typical performances of a conventional Warner brake/clutch including the inductor 178 and disc 134 are illustrated in FIGs. 7 and 8 of the drawings. For a set constant voltage V_war supplied to the solenoid 172, the magnetic force t?_magn attracting the disc 134 to the inductor 178 is a function of the distance, or "gap", between the disc 134 and the inductor 178 and varies as illustrated in FIG. 7 of the drawings. On the other hand, the F_magn, and consequently also the torque capacity of a Warner clutch/brake, varies for all practical purposes linearly with the voltage V_war as illustrated in FIG. 8 of the drawings. It should be noted here that the relation between F_magn and V_war is linear by design. Moreover, the following detailed explanation of the method for controlling the actuator system 170 is applied to a pull type starting friction clutch assembly 230 as illustrated in FIG. 2 of the drawings. FIG. 1 of the drawings illustrates only the components of the starting friction clutch assembly 230 illustrated in FIG. 2 of the drawings which interfaces directly with the clutch actuator 170 of the invention, i.e. the back plate 131/231, the diaphragm 132/232 and the housing 141/241. As it will be clear to one familiar with the art, the following analysis is applicable to diaphragm starting friction clutches of the push type, as well as to any clutch controlled by a thrust bearing. a/ The diaphragm 132 applies an axial force F_{d a} on the bolt 136 which is transformed by the ball ramp system 133/135/136 in a torque T_dla applied to the disc 134. This _dia is counterbalanced by the torque ^_bra_k created by the friction force 3?_brak existing between the disc 143 and the back plate 131. When V_war is equal to zero, the proportions of the system 170 are such that ^τ _bra_k ^^s higher than T_dla by a negligible amount, the system is therefore in a stable equilibrium, i.e. the disc 134 cannot rotate relative to the back plate 131. The exact equilibrium point would be reached when the following equation is satisfied: V₂ ^r ₂ ^{β r}ι tan (a) where r₂ helix radius a helix angle r₂ mean friction radius back plate/disc μ₂ coefficient of friction back plate/disc

The helix angle a necessary to obtain the equilibrium is a function of the mean radius of the helix r_{l f} the mean friction radius r₂ of the disc 134, as well as of the coefficient of friction μ₂ between the disc 134 and the back plate 131. It should be noted that the helix angle is independent of F_dla . The torque capacity of the starting clutch stays constant as long as V_var is equal to zero. Also it is noted here that the disc 134 does not move axially relative to the back plate 131 when V_war varies, only the force F_brak between them varies. b/ The spring 174, preferably but not necessarily a Belleville, is selected such that it forces the inductor 178 against the housing 141 with a force F_Belle after assembly. It is assumed that, for all practical purposes, F_{Be 2e} remains constant when the gap varies over its design range. When the maximum rated voltage, or "HV", is supplied to the solenoid 172, the inductor 178 pops out towards the disc 134 by the amount of the gap. As illustrated in FIG. 7 of the drawings, F_magn increases almost exponentially when the gap is reduced. c/ When the voltage supplied to the solenoid 172 is set at a second lower level, or "LV", the magnetic force F_magn is reduced to almost the value of F_Belle. If the voltage would be reduced further, the inductor 178 would pop out back towards the housing 141 since the Belleville spring is pulling it with a force equal to F_BeIIe and F_magn would drop further by approximately a factor of five as can be derived from FIG. 7 of the drawings. Since F_{d a} and ^F _bra_k ^{are not ec}J^ual ^tne difference is translated by the ball ramp into a torque r_ω which tends to force the disc 134 into rotation relative to the back plate 131, such that the force on the diaphragm F_dia is reduced.

Calculations indicate that r_ω is a function of F_Be22_e, ^aπd independent of F_d±_a , and it is evaluated as follows: ^rω^{= F}Belle ^2 ^r2 where r_ω decrease torque

^F _Belle Belleville spring force r₂ mean friction back plate/disc μ₂ coefficient of friction back plate/disc At LV, r_ω is at its maximum since, theoretically, there is no friction between the disc 134 and the inductor 178. If

F_magn is reduced further, the inductor 178 would pop out back towards the housing 141, and F-^-_JJ would drop by approximately a factor of five as it can be derived from FIG. 7 of the drawings. The rotational acceleration of the friction disc 134 consequent to the effect of T_rel is evaluated as follows:

• - i

where ώ acceleration of the disc r_ω decrease torque I rotational inertia of the disc It is noted that the rotational inertia I of the disc is low relative to r_re2, and therefore, ώ is relatively very high. When the magnetic force F_dia is equal to F_{Be 2e}' ^tne disc 134 rotates relative to the back plate 131 in a direction that reduces the load on the inner edge of the diaphragm 132.

The level of the magnetic force F_magn, which must be created by the inductor 178 in order to increase the diaphragm force to a level equal to F_dia will not be evaluated.

^Fmagn ^{m 2k F}dia + ^FBelle (* ' ^k) ^{w±th k m} V₂ ^r ₂/V₃ ^r3 where ^Fmagn magnetic force

^F _{d a} f°^rce diaphragm

^F _Be_lle Belleville spring force r₂ mean friction radius back plate/disc μ₂ coefficient of friction between back plate/disc r₃ mean friction radius disc/inductor μ₃ coefficient of friction between disc/inductor

As a numerical example, it may be assumed that the maximum force F_{d a} applied to the inner edge of the diaphragm is equal to ten times the force F_Be22β °^ the Belleville spring, and that k is equal to 1/5. Using the last equation, and since minimum of F_magn is reached when F_dla becomes equal to F_Bβ22e, the magnetic force F_magn varies between the following minimum and maximum values over the range of variation of F_dia t

(^Fmagn) max ^{= 4} ' ^{8 F} Belle ^and (^Fmagn)min ~ ^{l 2} ^F Belle where ^Fma_gn magnetic force developed by the inductor

^F _Be_lle Belleville spring force

If it is assumed that initially the force F_dia is equal to

^F _Be_lle ^anc that no power is supplied to the solenoid 172 and if F_magD is increased from zero to its maximum, the disc 134 rotates relative to the back plate 131 until F_dia is raised to 10* F_Belle. If F_magn is increased to its minimum, F_dia remains at its initial level and equal to

^F Belle' e/ The relation between the axial travel and the force F_dla applied on the inner edge of the diaphragm 132 by the ball ramp is as illustrated in the FIG. 9 of the drawings for present conventional diaphragm based starting friction clutches 230 like the one illustrated in the FIG. 2 of the drawings. It should be noted that the torque capacity of the starting clutch has already reached zero before the maximum ordinate of the force F_dia is

' reached, and at that time the travel is approximately 25% of the maximum. It is simpler control wise, but not necessary, to set the maximum of the magnetic force F_magn to such a level that the corresponding value of F_dia stays below its maximum as illustrated in FIG. 9. .And this, because with a one-to-one relation, for each level of F_magn, corresponds approximately a single value for the torque capacity of the starting clutch. f/ Alternatively, instead of using a single solenoid as illustrated in FIG. 1 of the drawings, the coil of the single solenoid 172 can be separated into two distinct solenoids, each having its own power supply, and the number of turns of the wiring of each of the two solenoids is adjusted such that when a same constant voltage V_war is supplied to one or to both, the resultant magnetic force ^Fm_agn ^is either equal to F_Belle or to 4.8 F_Belle. This alternate solution is advantageous in the way that it allows pulse width modulation ("PWM") of the power supplied to both solenoids using only one stabilized source of voltage.

The method according to the invention for controlling the clutch actuator system 170 will be described in detail hereunder in reference to the general analysis of the clutch actuator system illustrated in FIG. 1 of the drawings and performed above. Assume that the vehicle engine is rotating, and that initially, the torque capacity of the starting clutch, as well as the voltage V_war supplied to the solenoid 172, are both equal to zero. FIG. 10 of the drawings illustrates, as an hypothetical example only, how the voltage V_war applied to the solenoid 172 may vary relative to the time t. Step 1: the maximum rated voltage HV is applied to the solenoid 172. The inductor 178 pops out against the disc 134, and the maximum rated friction torque is created between the disc 134 and the inductor 178. This level of torque tends to decrease the torque capacity of the starting clutch to zero, but it is already fully open, so the load on the inner edge of the diaphragm does not change.

Step 2: the solenoid is supplied with a PWM electrical current, which voltage V_war can be toggled between two specific levels, either HV or LV. As we have seen before, when LV is supplied, the disc 134 tends to rotate relative to the back plate 131 in such direction that the torque capacity of the starting clutch tends to be reduced, and when HV is supplied, the disc 134 tends to rotate relative to the back plate 131 in the opposite direction, such that the torque capacity of the starting clutch tends to be increased. Since it takes a finite amount of time for the disc 134 to rotate relative to the back plate 131, primarily because of its own rotational inertia, it is possible, by varying the width and the time between two pulses at a relatively high frequency, to modulate precisely the starting clutch, and set the variation of the torque capacity as a function of time as required, until the torque capacity of the starting clutch becomes maximum. The switching from LV to HV and backwards, is triggered by the computer system 650 depending if the torque capacity must be decreased or increased respectively. The terms "increase", "decrease" and "no change" illustrated in FIG. 10 of the drawings, are a reference to the force applied to the diaphragm 132 by the ball screw 133 of the starting clutch at various levels of V_war. It should be noted here that with this method, at any time during the step 2, the torque capacity of the starting clutch is either in the state of being increased or decreased. However, it should be noted that as long as, the length of time between two pulses, or the length of time of a pulse, are relatively very short, the disc 134 rotates by a relatively very small amount, since the amount of its rotation relative to the back plate 131 increases with the square of the time. The gap between the disc 154 and the back plate 131 stays always at zero during the all the length of time the starting clutch is being modulated. Therefore, neither the disc 134, nor the inductor 178, move axially during the modulation of the starting clutch, only the pressure varies within the two friction surfaces of the disc 134. Therefore there is practically no time lag between a variation in the magnetic force and the variation in the pressure in the two friction surfaces of the disc 134, insuring a relatively extremely fast response of the clutch actuator system 170.

Step 3: no power is supplied to the inductor 178, with the result that the inductor 178 pops back towards the housing 141, and the torque capacity of the starting clutch at the level it reached last, for as long as electrical power is not supplied to the inductor 178.

Step 4: the maximum rated voltage HV is applied to the solenoid 172, with the result that the inductor 178 pops towards the disc 134, and the ensuing friction torque created between the disc 134 and the inductor 178 rotates the disc 134 relative to the back plate 131 until the starting clutch gets fully open again.

FIG. 2 of the drawings is a schematic sectional view illustrating a preferred embodiment of the working components of the starting clutch actuator 270 system and gearbox actuator system 280 of the invention. This system actuates electronically and controllably, at the same time, the starting clutch 230 and the gearbox 640. The starting clutch actuator system 270/370 is schematically illustrated in the FIG. 3 of the drawings and the gearbox actuator system 280/480 is schematically illustrated in the FIG. 4 of the drawings. In this embodiment, the starting clutch actuator system 270 preferably powers the gearbox actuator system 280 through a belt 226 and pulley 224/225 system, or any other appropriate means known in the art. It should be noted here that the pulley 225 is powered by the vehicle engine by maintaining the clutch actuator 270/370 in an energized state, after the starting clutch 230 is opened, in order to couple the pulley 225 to the engine driven, rotatable back plate 231 in a manner to be described in more detail below.

The FIG. 3 of the drawings is a partial and scaled up view of FIG. 2 of the drawings, illustrating and alternative embodiment of the starting clutch actuator system 370 of the invention. The actuator system 370 is intended to operate electronically and control the opening and the closing of a starting friction clutch assembly 230 of the type commonly used in vehicles, particularly for passenger cars, as well as supply mechanical power to the gearbox actuator system 480. The starting clutch actuator system 370 of this invention has the same axis of revolution 343 as the axis 243 of the starting friction assembly 230 illustrated in FIG. 2 of the drawings, and comprises an electronically operated magnetic brake/clutch system, and a mechanism transforming a rotational movement into an axial displacement, such as non-limiting examples, ball ramp and ball screw systems, or any other system known in the art. The magnetic inductor 378 includes a solenoid 372, surrounded by a breech 371 and a body 373, both having a high magnetic permeability. Electric power is supplied to the solenoid through the wires 351, and a pulley 324 is fastened permanently by adequate means to the breech 371. One or more banana slots 375 are machined on the friction surface of the breech 371 facing the disc 334, such that the breech 371 tends to attract the disc 334 magnetically when electrical power is supplied to the solenoid 372. The body 373 has the shape of a spool and is located radially by a journal surface 376 relative to the breech 371, allowing the breach 371 to rotate and slide axially relative to the body 373. The body 373 is bolted to the gearbox housing by bolts 342, or any other adequate means. The body 373 and the breech 371 are brought together axially under a relatively low axial force by a spring like washer 374. The disc 334 is in friction engagement with the friction pads 338 of the back plate 331. In the embodiment illustrated in FIG. 3 of the drawings, the screw 333 and bolt 336 are of the ball screw type. The system is such that when the screw 333 rotates relative to the bolt 336 in one rotational direction, the diaphragm 332 is pulled toward the back plate 331, opening the starting clutch 230, while when the screw 333 rotates in the opposite relative direction, the starting clutch diaphragm moves away from the back plate 331 and the starting clutch 230 is closed. To describe the functioning of the vehicle starting friction clutch actuator system 370 of Figs. 2 and 3, it is assumed that the starting clutch 230 is initially in the open position, and consequently, that the diaphragm spring 332 has been pulled away from the engine, or to the right-hand side of Fig. 3, by the bolt 336 reacting on the screw 333. It is also assumed initially that a resisting torque is applied by the belt 226 on the pulley 324 to preclude rotation of the breech 371, as will be described in more detail below with reference to Fig. 4. The lead of the ball screw system and the friction coefficient of the material of the friction pad 338 are selected so that the torque tending to rotate the screw 333 under the effect of the axial force applied by the diaphragm spring 332 on the bolt 336 is counterbalanced by the friction torque generated between the disc 334 and the friction pad 338, which means that the screw 133 and the bolt 136 cannot rotate relative to each other. However, as soon as an electric current is supplied to the solenoid 372 through the wires 351, the magnetic field created by the solenoid 372 tends to attract the disc 334 magnetically. However, the breech 371 is held by the spring 374 away from the disc 334. It should be noted

relative to each other, and the diaphragm 332 is pulled towards the back plate 331, and this until the starting clutch 230 is fully opened. The amount of release of the starting friction clutch can be controlled by varying the amount of power supplied to the solenoid, since for each level of power, corresponds a level of torque applied by the breech 171 on the disc 134, and therefore a level of axial force applied to the diaphragm spring 332.

Since the actual torque capacity of the starting clutch 230 varies, in the range of utilization of the system 370, almost linearly with the force applied on the diaphragm 332 by the bolt 336, and since each level of electrical power supplied to the solenoid 372, corresponds a level of force applied to the diaphragm 332, the torque capacity of starting clutch 230 varies with the amount of power supplied to the solenoid 372. This feature is particularly useful when it is necessary to maintain a certain speed differential between the engine 660 and the input of the gearbox 640, since the starting clutch must be in this case constantly released slightly or, engaged further by small amounts.

It is to be noted that the electronically operated magnetic brake/clutch functions only as a brake during the starting clutch 230 actuation, since the breech is held by the pulley 224 as will be described in more detail below. In FIG. 4 of the drawings is illustrated the preferred embodiment of the gearbox actuator system 280/480 of the invention, designed to select and engage the speed ratios of a gearbox 640. To simplify the description of the starting clutch actuator system 370 of the invention, and since the arrangement of the control rod 644 protruding from the gearbox 640 has no effect on the objective of the invention, it will be assumed throughout this application, that the gearbox is of the type having a single control rod 644 protruding from the gearbox 640 perpendicular to the axis of revolution 243 of the gearbox 640, and that the synchronizers (not shown) are actuated by the axial movement of the control rod 644, and the various fork rods (also not shown) are selected by the rotation of the control rod 644. However, the arrangement of the external control of the gearbox has no effect on the true meaning of the invention. It is also assumed that an internal interdiction mechanism, precludes the rotation of the control rod 644 as long as the control rod 644 is not in its middle axial position, or the Neutral position. The interdiction mechanism is almost universally adopted in present manually operated gearboxes, and will not be described here since it is well known in the art. The gearbox actuator system 480 has an output rod 285/485 which is intended to actuate the gearbox control rod 644 and control ratio shifting of the vehicle gearbox 640, replacing the action of a conventional hand operated shift lever. The movements of the output rod 285/485 and of the control rod 644 are linked by adequate means, which, since it is assumed that the control rod 644 is perpendicular to the gearbox axis 243, i.e. parallel to the output rod 285/485, may be an external lever 286 at the end of each of the of the shafts, the levers 286 being connected together axially and rotatably by a wide rod 229 capable of transmitting, at the same time, the axial and rotational movement between the two shafts, like in the 1993 SAAB 900.

The gearbox actuator system 480 is contained in a housing 481 fastened by adequate means to any convenient part of the vehicle, and may include the gearbox 640, although alternatively, the actuator system 480 can be integrated inside of the gearbox 640, in which case the output rod 485 and the gearbox control rod 644 may be one part.

The fork rods are actuated by the axial movement of the output rod 485. As discussed before, this actuation requires a relatively high level of power, and according to the invention, this power is mechanically delivered by the engine of the vehicle, through rotation of the pulley 425. Preferably, but not necessarily, the pulley 425 is driven by the reaction member 371 of the starting clutch actuator system 370 through a belt 226, as will be described.

The rotational movement of the pulley 425 is transformed in an alternating axial movement of the output rod 485 by adequate means. In a preferred embodiment, the means is in the form of a crank and connecting rod mechanism. The crankshaft 482, driven by the pulley 425, is journaled on the housing 481 and its crank has an axis 487. The small end of the connecting rod 483 drives the output rod 485 axially back and forth through a mechanical interface having two degrees of freedom, as an example, but not limited to, a spherical ball and socket mechanism 484. The pulley 425 can be releasably grounded to the housing 481, preferably by the action of an electromagnetic brake 423 of the WARNER type, having a solenoid 421, bolted, or otherwise fastened by adequate means, to the housing 481. When the solenoid 421 is supplied with electrical power, it attracts magnetically the disk 422 of the pulley 425 against the friction surface of the brake 423, grounding it to the housing 481. The mechanism utilized for the selection the fork rods is illustrated schematically in the FIG. 4 of the drawings as being a power screw including a worm gear 488 fixed axially by the housing 481 and in mesh with a worm pinion 489 driven preferably, but not necessarily, by an electric motor (not illustrated). The size and power of the electric motor is relatively low, since the power required for the selection of a fork rod is relatively low. Because the combined rotating inertia of the output rod 485 and the gearbox selector shaft are relatively low, and the rotation of these shafts between two consecutive fork rods, only a few angular degrees. The worm gear 488 drives rotatably the output rod 485 through a sliding key 487, such that the output rod 485 is free to move axially.

It should be noted here that the means for the actuation of gearbox fork rods, as a non limiting example, the crank and rod mechanism described hereupon, and the means for the selection of fork rods, as a non limiting example, the power screw mechanism hereupon, can be separated, which may be more practical in some instances, for example when the gearbox has two selector outer levers instead of a single one.

The rotational and axial position of the output rod 485 can be detected by various means known in the art, including as a non limiting example, a series of micro switches which can take either the "On" or the "Off" position. These micro switches are mounted by adequate means, preferably radially, but not necessarily, around the output rod 485. One of these micro switches is illustrated and designated by reference numeral 428. A series of spherical holes are drilled on the periphery of the output rod 485, such that the status of these micro switches change from the On to the OFF position, or the opposite, when their end detector reaches one of these holes. With a relative low number of micro switches, the computer 650 can calculate at which of the large number of possible axial and rotational position the actuator selector shaft lies at any given time, by analyzing the status of all micro switches at that time. Alternatively, these micro switches can be mounted around the gearbox outer lever. To describe the functioning of the gearbox actuator system 480 an upshift from third to fourth will be first described. The rotational position of the output rod 485 corresponds to a fork rod which actuates together the third and the fourth gear ratio, identified as 3-N-4, which means that this shift does not involve a change of fork rod. Therefore, the connecting rod 483 can move the output rod 485 axially, which in turn, moves the fork rod axially, from the third speed ratio position towards the fourth ratio position, through the Neutral position. Electric power is supplied initially to both the solenoid 372 of the starting clutch actuator system 370 and to the solenoid 421 of the WARNER electromagnetic brake, holding the pulley 425 rotatably locked to actuate only the starting clutch. When the computer system 550 calculates that the starting clutch 640 is fully open, the power to the solenoid 421 is interrupted, and the power supply to the solenoid 372 of the starting clutch actuator system 370 is set to the desired level, depending on the temperature of the gearbox, and/or other parameters, such as the position of the accelerator pedal, the engine speed, etc., since that electrical power level determines how much force is applied to the output rod 485, and therefore how fast the synchronizers are actuated. When the output rod 485 reaches its desired axial position, which is assumed here to be the fourth speed ratio position, the electric power supplied through the solenoid 372 of the starting clutch actuator system 370 is interrupted, and the mechanisms existing in present gearbox systems keeps the speed ratio locked in position.

To describe further the functioning of the gearbox actuator system 480 an upshift from fourth to fifth will be described, an upshift which involves a change of fork rod, specifically from a fork rod controlling 3-N-4 to a fork rod controlling 5-N-6. It should be noted here that in present transmissions, by construction, as long as the internal selector of the gearbox 640 is not in its axial NEUTRAL position, it cannot be moved to select a different fork rod, which means that the internal selector of the gearbox 640 cannot be rotated. But in present transmissions, an elasticity is built in, by design, between the selector and the gearbox control rod 644. It may be necessary in certain gearboxes to increase this flexibility, enough to allow the worm wheel 488 to be forced rotatably by the worm pinion 489 to the position corresponding to the two adjacent fork rods, when required.

As the first step of this upshift, the electric motor driving the worm pinion 489 is powered and rotates the worm gear 488, taking out the springy backlash.

Thereafter, power is supplied at the same time to the solenoid 372 of the starting clutch and to the solenoid 421 of the brake 423, and when the starting clutch 230/630 is fully open, the power to the solenoid 421 is interrupted, the pulley 486 can rotate, and the output rod 485 is moved axially towards the Neutral position, at which time, the internal selector of the gearbox becomes free to jump to the 5-N-6 rotational position under the elastic energy accumulated between the selector and the worm gear 488. In a preferred embodiment, at that time the direct current supplied to the solenoid 372 through the wires 351 is cut, until the output rod 485 gets in its rotational position 5-N-6, and restored thereafter, in order to move axially the output rod 485 further, until the sixth ratio becomes fully engaged, at which time the power supplied to the solenoid 372 is cut again. In this case, the starting clutch 230/630 stays open during the time the output rod 485 stays in the Neutral position, whereas alternatively, particularly for a downshift, the starting clutch 230/630 can be closed, by supplying pulsating current, and thereafter opened by a direct current. This last case simulates the double declutching shifts, in which the starting friction clutch is closed when the shift lever is in Neutral, and opened again to be moved to the next speed ratio. This method has the advantage to reduce the strain on the synchronizers, and accelerate the synchronization process, as long as the vehicle engine is also controlled by the computer 650 and accelerated or decelerated to the next ratio speed level by adequate means, which may include without limitation, an action on the fuel injection system, the ignition system and the camshaft phase.

A speed ratio shift between two consecutive speed ratios corresponding to a same axial position of the output rod 285, for example, as it is often the case, between the first ratio and reverse, for which one rotational position of the output rod 285 corresponds to l-N-2, and the other to R-N. In this case, the transmission must be shifted from first to second ratios, and then, from second to reverse, as described previously, but, the starting clutch is kept open during these two consecutive shifts.

In reference to the FIG. 5 of the drawings, therein is illustrated an alternate embodiment of a gearbox actuator system 580, designed to select and engage the speed ratios of a gearbox 640 and to be integrated into its housing 541, with the result that the output rod 285/485 of the actuator system and the control rod 544 of the gearbox previously described and illustrated, are one part. The rotational movement of the pulley 526 is transformed in an alternating axial movement of the gearbox control rod 544 by a cam 582, similar to the cams of an engine camshaft. The cam 582, driven by the pulley 525, is journaled on the gearbox housing 541. The cam actuates axially and alternatively the gearbox control rod 544 through a U beam 583 fastened by adequate means in a slot machined to the control rod 544. The power screw mechanism is on the end of the control rod 544, its cover 541' being fastened by adequate means to the gearbox housing 541. The functioning of the system is the same as for the preferred embodiment illustrated in the FIG. 2, 3 and 4 of the drawings, and therefore it will not be described.

FIG. 6 of the drawings is a schematic illustrating the working control components, and the electrical control components of the electronically actuated and controlled power transmission system of the invention. This schematic assumes that the vehicle computer 650 controls various functions of the vehicle and the engine, in addition to the control of the starting friction clutch and the gearbox. Only the minimum set of functions specific to the control of the starting clutch and of the gearbox are illustrated and described hereunder.

The vehicle powertrain form to include an engine 660, a starting clutch system 630, a multi-speed multi-layshaft gearbox system 640, the output shaft 647 of the gearbox system 640 driving the vehicle ground wheels through appropriate means.

The electrical control components form to include, the vehicle battery 665, the ignition switch 666, a ratio/range selector system 690 having at least the positions Drive/Neutral/Reverse, a computer system 650 illustrated in block diagram and composed of a power supply 667, a logic board 654 with a clock, a series of input boards 653 and a series of output boards 655. It is assumed here that the computer system 650 controls also the engine fuel injection and ignition. Only those electrical control components which are directly necessary to the functioning of the electronically actuated and controlled power transmission system are illustrated. The input boards 653 have signal converters for processing computer system 650 inputs, these input signals being generated by sensors and detectors, all well known to one skilled in the art, these inputs forming to include, the vehicle speed sensor connected by the electrical wiring 658, the position sensors of the hand operated shift lever, connected by the electrical wiring 657, the sensors, preferably, but not necessarily, micro switches, giving the position of the various fork rods through the detection of the axial and rotational position of the gearbox selector shaft, or, of the output rod 485 of the gearbox actuator 480 connected by the electrical wiring 656, the engine throttle position sensor connected by the electrical wiring 663, and the engine speed sensor connected by the electrical wiring 661. The output boards 655 have power amplifiers to develop appropriate computer system 650 outputs, these outputs forming to include, the control power for the solenoid 172/372 is supplied by the wiring 651, the control power for the solenoid 421 is supplied by the wiring 659, and the control power for the electric control motor driving the power screw 489/489 is supplied by the wiring 652.

It should be noted here that the electromagnetic Warner system embodiment of Figs. 2 and 3 functions as a controllable clutch for the gearbox actuator system 280/480, by transmitting, in effect, the engine power to the pulley 225/425 of the gearbox actuator system 280/480. The output power of the vehicle engine 660, for example, is transmitted through the pulley 224 frictionally engaged for rotation with the back plate 231, through a belt 226, to the pulley 225/425/525 of the gearbox actuator system 280/480/580. Also, the brake 423 of the gearbox actuator system 280/480/580 functions as a brake for holding the pulley 324 and the breech 371 against rotation for the described operation of the clutch actuator system 370. It is contemplated, however, that the clutch actuator 170 of Fig. 1 could be used with the gear actuator system 280/480/580 by bolting the pulley 224 to the back plate 131 of the starting clutch 230.

Also, the mechanism utilized for the selection of the fork rods, the power screw 488/489, can be separated from the synchronizer actuation mechanism of the gearbox actuator system 480, which is particularly obvious when the gearbox system 640 has two separate control rods, one for the synchronizer actuation, and the other for the selection of the fork rods.

FIG. 11 of the drawings is schematic half-sectional view illustrating an alternate embodiment of the working components of the starting clutch actuator system of the invention. The actuator system 1170 is similar to the actuator system 170 described in FIG. 1 of the drawings and will, therefore, not be described in detail, except for the components which are modified or added. In accordance with the reference numeral convention used throughout this text, the last two digits of the reference numeral designating similar parts are common to FIGs. 1 and 11 of the drawings. In the alternate embodiment of the actuator system 1170 of the invention, the inductor 1178 is encased in a holder 1117. The holder retains the inductor 1178 axially and radially, but allows the inductor 1178 to rotate relative to the holder 1117. The holder 1117 is secured relative to the housing 1141 in the same manner as the inductor 178 is secured to the housing 141 as illustrated in FIG. 1 of the drawings, that is, through a Belleville spring 174/1174 riveted to the inductor 178/1178 on one hand, and secured to the housing 141/1141 by bolts 142/1142 on the other hand, such that the inductor 178/1178 can move axially when magnetically attracted by the disc 134/1134.

Electrical power is supplied to the solenoid 1172 by appropriate means known in the art, such as for example, brushes and slip rings (not illustrated) . The inductor 1178 can be rotated controllably relative to the holder 1177 by adequate means known in the art. Since the friction torque applied by the disc 1134 to the inductor 1178 is always in the same rotational direction, a suitable means to rotate the inductor relative to the holder may include, as a limited example only, a cable 1127 fastened to the breech 1171 and wound around the breech 1171. In a preferred embodiment, the cable 1127 is pulled together with the cables of the vehicle hand operated parking brake. As a result, each time the parking brake is applied, the inductor 1178 is forced to rotate relative to the holder 1117, the resulting amount of rotation of the inductor 1178 relative to the holder 1117 being equal or greater than the amount of rotation of the screw 1133 relative to the bolt 1136 necessary to bring the torque capacity of the starting clutch 630 from its maximum' torque capacity position to its zero torque capacity.

The addition of the holder 1117 addresses a problem that arises when the vehicle becomes immobilized in gear while the starting clutch 630 is closed. In this situation, the torque capacity of the starting clutch 630 must be brought to zero before the engine can be restarted. This is achieved by the computer system 650 supplying direct or alternate electric power to the solenoid 1172 at the maximum rated level, which has the effect of increasing the pressure between the inductor 1178 and the disc 1134 to its rated maximum. Thereafter, as soon as the vehicle operator applies the vehicle parking brake the starting clutch 630 opens, since when the cable 1127 is pulled, the inductor 1178 is forced to rotate relative to the housing 1141, which in turn, forces the rotation of the screw 1133 relative to the back plate 1131, since the back plate 1131 is immobilized, and since the vehicle engine 660 is not rotating at that time. The end result is that the torque capacity of the starting clutch 630 is progressively brought to zero when the inductor 1178 is forced to rotate when the cable 1127 is pulled, at which time, the engine 660 can be started again safely. Otherwise, as long as the vehicle engine is rotating, the system described according to FIG. 11 of the drawings is operated by the methods described above with reference to FIGs. 1, 7, 8, 9 and 10 of the drawings. It is to be clearly understood that the present invention is not to be limited to the embodiment shown and described herein, but is susceptible to numerous changes and modifications as it will be apparent to one skilled in the art.

Without departing from the true spirit of the invention, the means to rotate the inductor 1178 relative to the holder 1117 can be a non reversible power screw driven by an electric motor (not illustrated) controlled by the computer system 650. In this case the screw is integral with the electric motor shaft, whereas the gear is machined on the breech 1171.

In the first embodiment of the invention, described above with reference to FIG. 1, it was noted that the bias of the starting clutch diaphragm 132 is in a direction away from the backplate 131, or to the left as shown in FIG. 1. As a result, the disc 134 is held against the friction pads 138 on the rear of the back plate 131 under the bias force of the diaphragm 132. In FIG. 12, a variation in the embodiment of FIG. 1 is shown and which is intended for use with starting clutches in which the bias of the diaphragm is reversed, or to the right as viewed in FIG. 12.

In the actuator system 1270, the disc 1234 is located centrally on a sleeve extension of the screw 1233 to be frictionally engaged with the front surface of the backplate under the bias force of the diaphragm 1232. The inductor 1278 is again supported by a Belleville spring 1274 from the housing 1241, but within the housing to be movable axially away from the backplate against the force of the spring 1274. A magnetically permeable disc 1234' is fixed to the rear end of the sleeve extension of the screw 1233. Thus, actuation of the inductor 1278 will be effective to pull the disc 1234' and the sleeve extension toward the backplate 1231 and reduce pressure between the friction disc 1234 and the backplate 1231 against the bias force of the diaphragm 1232. In all other respects, operation of the servomechanism system 1270 is the same as the system 170 of FIG. 1.

It will be also appreciated that modifications and/or changes may be made in the described embodiments, without departure from the invention. Accordingly, it is to be understood that the foregoing illustrations are illustrative of preferred embodiments only, not limiting, and that the true spirit and scope of the present invention will be determined by reference to the appended claims. In light of the foregoing description and accompanying drawing illustrations, it will be appreciated that as a result of the present invention, a highly effective electronically actuated and controlled power transmission system is provided by which the aforementioned objectives are completely fulfilled.

Claims

What is Claimed is:

1. In an automotive drive train having an engine with a rotatable power output, a starting clutch having a rotatable starting clutch input including a backplate and driven by the power output of the engine, and a rotatable starting clutch output, the starting clutch being adjustable between zero and maximum torque transmitting capacity, and having an axially biased movable control member for controlling the torque transmitting capacity, a servomechanism for operating the starting clutch, comprising: a torque to linear force conversion device coupled to said axially movable control member to adjust the actuating force of the starting clutch reversibly between zero and maximum; a rotatable friction device normally retained in frictional torque transmitting engagement with said back plate by the axially biased movable control member, the rotatable friction device being connected to said torque to linear force conversion device to counter balance feed back torque converted from linear force of the axially biased moveable control member; and an electromagnetic device to control the torque transmitting engagement of the friction device with the back plate in a manner to operate said torque to linear force conversion device to move said control member for actuating the starting clutch.

2. The automotive drive train recited in claim 1, including means for supporting said electromagnetic device for axial movement toward and away from said rotatable friction device under a bias force urging the electromagnetic device away from the rotational friction device.

3. The automotive drive train recited in claim 2, wherein said means for supporting said electromagnetic device comprises a spring connected between said electromagnetic device and a fixed housing part.

4. The automotive drive train recited in claim 1, wherein said electromagnetic device comprises an inductor having a magnetically permeable breech of annular configuration, a solenoid coil concentric with said breech, a body fixed to said solenoid coil, and a spring washer connected between said body and a fixed housing part.

5. The automotive drive train recited in claim 4, wherein said breech is fixed to said body and to said solenoid coil.

6. The automotive drive train recited in claim 4, wherein said breech is rotatable relative to said body and said solenoid coil.

7. The automotive drive train recited in either of claims 4, 5, or 6 wherein said breech includes a friction face engageable with said rotatable friction device and having banana slots in said friction face.

8. The automotive drive train recited in claim 6 including a brake for releasably retaining said breech against rotation.

9. The automotive drive train recited in claim 1 comprising means for operating the electromagnetic device to reduce the torque transmitted between the rotatable friction device and the backplate so that the forces of the axially biased movable member cause relative rotation between the backplate and the rotatable friction device.

10. The automotive drive train recited in claim 1 wherein the electromagnetic device comprises an inductor including a solenoid coil and a breech having a friction face, the inductor being supported so that said friction face is normally spaced from contact with said friction device.

11. The automotive drive train recited in claim 10 including means for operating said inductor to reduce the torque transmitted between the rotatable friction device and the backplate so that the forces of the axially biased movable member cause relative rotation between the backplate and the rotatable friction device in a direction to adjust the starting clutch toward maximum torque transmitting capacity.

12. The automotive drive train recited in claim 10 including means for operating said inductor to release torque transmitting engagement between the rotatable friction device and the backplate and engage said friction face with said friction device to over come the forces of the axially biased movable member and cause relative rotation between the backplate and the rotatable friction device in a direction to adjust the starting clutch toward zero torque transmitting capacity.

13. The automotive drive train recited in claim 12 including a multiple speed ratio gear box, a movable shifting member to shift the speed ratio of the gear box, and a rotatable drive element coupled to said breech to transmit engine power to said shifting member when the friction face of said breech is in engagement with said friction device and the starting clutch is adjusted to zero torque transmitting capacity.

14. The automotive drive train recited in claim 13 further including a brake engageable with said rotatable drive element to retain said breech against rotation when the starting clutch is adjusted to maximum torque transmitting capacity.

15. The automotive drive train recited in claim 1 wherein said electromagnetic device comprises a rotatable inductor having a friction face in torque transmitting relation with the rotatable friction device, and including means for rotating said rotatable inductor and the rotatable friction device independently of the engine output power. magnetically permeable breech of annular configuration, a solenoid coil concentric with said breech, a body fixed to said solenoid coil, and a spring washer connected between said body and a fixed housing part.