DE3513279C2 - Automatic gear shifting device - Google Patents

Description

The invention relates to a device for automatic Switching of a multi-gear connected downstream of a drive motor Gear change transmission for vehicles, especially motor vehicles, according to the preamble of claim 1.

A significant potential for reducing fuel consumption of vehicles, in particular of passenger cars, lies in the better utilization of the areas of favorable engine efficiency by choosing the cheapest gear ratio under incl drawing a longer maximum translation.

The already known switching and consumption display in connection with a 5-speed gearbox, in which the fifth gear as a long gear with overdrive translation shows at correct application, a significant reduction in fuel consumption. The more frequent switching work required for this, especially for the additional gear, but burdens the driver. Another difficult one speed of such a 5-speed transmission is that another shift alley is present, the operation of such a manual switch gear takes getting used to.

Conventional automatic gearboxes, where the switching effort is essential offer, on the other hand, generally offer despite increased technical Effort too few gear stages with a relatively bad result  Efficiency.

Against this background, a dome is from DE-PS 7 38 517 lungseinrichtung known in which the torque by claws is transferred, the driving areas in the direction of the order are inclined that the claws of both coupling parts maintain their position in relation to each other with positive torque. The se known coupling device also prevents with the help of Springs until a preselected negative torque is reached mentes a sliding against each other and thus a disengaged com claws. The coupling device serves as a switch-off re coupling device between two coaxial arranged, axially displaceable and rotating Coupling parts, with wedge-like in the axial direction, steep helical profiles for the purpose of torque transmission, especially in power plants where two or several motors working on a common drive shaft ten.

The object underlying the invention is a Device for the automatic switching of gear change driven by vehicles to create a conventional use cher, so-called mechanical manual transmission enables and consequently a simpler structure and a cheaper one Offers efficiency.

This problem is solved in accordance with the characteristics of Pa tent Claims 1. The use of a conventional Schaltge drive with coupling links that correspond to the engagement of the Corresponding gears are operated by a servo control device and as long as a certain min applied by the engine residual tensile moment is present, by holding in the indented Remain in position and only when a minimum train is undershot To disengage the moment automatically, compared to conventional ones Chen manual transmissions only require a little additional effort to adapt the coupling links and to provide a simple servo adjustment required. Here are the Coupling links made of engagement teeth Sliding sleeves formed, each pre-featured on the idler gears drive teeth can be brought into engagement. Except at least have the train lying next to each other during train operation flank such gears such an undercut angle that during the application of one above a minimum value lying tensile torque of the drive motor the gearing holding forces are generated. Close are means for applying a to the sliding sleeves at least temporarily and then continuously acting off provided that the force falls below the minimum tensile mo automatically disengaging the gearing.  

Expedient embodiments of the invention are the subject of the rest Subclaims in connection with the description of the in the Drawing illustrated embodiment of the invention explained in more detail become.

The drawing shows in

Fig. 1 is a schematic diagram of an internal combustion engine having the inventive automatic gearshift device,

Fig. 2 is an illustration of the servo actuator for actuating the coupling members and

Fig. 3 is an enlarged view of the Zahnein handle of the coupling members.

In Fig. 1 of the drawing, 1 denotes a conventional, example, four-cylinder, spark-ignition reciprocating internal combustion engine, which is used as a drive motor for a passenger vehicle. With 2 an internal combustion engine downstream transmission is indicated, which, as is not further shown here, has in a conventional manner several gear pairs, each assigned to a gear, with sliding sleeves suitable for engaging these gear pairs, which can be actuated by adjusting a shift rod 7 . 3 denotes a differential gear driven by an output shaft of the transmission 2, each with a drive half shaft 4 leading to the two drive wheels of the vehicle, not shown here.

To actuate the transmission 2 , which in principle is designed like a conventional manual transmission except for a few features to be described later, a shifting rod 7 adjusting the shifting device 6 is used with a z. B. pneumatic Servostellein device 10 with actuators 11 a, 11 b and 12 , the pressurization of which is controlled by electromagnetic valves 13 to 16 as a function of signals from the control unit 5 . 8 also indicates a drive range selector lever, with the aid of which a forward drive range D in which the individual forward gear stages are automatically switched on, a neutral position N in which no gear is engaged, and a reverse drive stage R in which a reverse gear is mechanically engaged, is adjustable. If necessary, a parking position to be selected with the range selector lever 8 could also be seen here, in which, as is known from automatic transmissions, a mechanical lock for blocking a transmission shaft connected to the drive wheels of the vehicle is engaged.

In the drawing, the servo control device 10 has been shown to work with excess pressure, 18 denoting a pressure accumulator which can be refilled from a pressure source 17 , for example an air pump. An intermediate overflow valve 19 has the task of filling up the reservoir 18 only when the minimum pressure in the rest of the system has been reached. With this system pressure stored in the memory 18 , the actuators 11 a, 11 b and 12 of the servo actuating device 10 as well as any other actuators that may be present but not shown here can be acted upon.

To obtain the control signals required for the control of the gearshift device 6 , the control unit 5 can receive actual values from various sensors 20 and 23 to 26 that detect certain characteristic state variables of the internal combustion engine or the vehicle. Thus, 20 represents a sensor for the intake manifold vacuum, which is arranged in the intake line 22 behind a throttle valve 21 , which can be adjusted in a known manner to adjust the power of the internal combustion engine 1 by actuating an accelerator pedal, not shown here. 23 denotes a sensor that detects the engine speed or the speed of the input shaft 27 of the transmission 2 , while 24 denotes a speed sensor that detects the output speed on the differential 3 . 25 denotes an encoder that detects the gear stage of the transmission 2 that is currently switched on, and finally 26 denotes an encoder that detects the position of the travel range selector lever 8 . Instead of the vacuum sensor 20 , a transmitter for the direct detection of the position of the accelerator pedal could also be provided, and the speed sensors 23 and 24 could also be arranged at locations other than those specified. So it would be possible, for example, the inductive sensor 23 to detect the engine or transmission input speed instead of the starter gear 29 of the flywheel 28 also with a gear shaft on the gearbox 27 held gear gear of the transmission 2 in a manner known per se to form a Let the speed measured value work together.

In FIG. 2, the shifting apparatus is schematically shown in an enlarged scale. 6 Thereby, from this figure of the drawing is seen that the switching rod 7 with two shift fingers 35 and 36 is provided which for switching the transmission gears each with an associated by several, each with a transition pair of shift forks 37 to 40 which actuate the associated with this gear pair of shift sleeves , come into engagement. The shift finger 35 engages the shift forks associated with the forward gears 37 to 39 , while the shift finger 36 can be brought into engagement with the reverse gear shifting fork 40 , this engagement of the shift finger 36 only by hand, namely by actuating the Fahrbe range selector lever 8 in the position indicated by broken lines, takes place.

The engagement of the forward gears, of which five are to be provided in the exemplary embodiment shown in the drawing, takes place completely automatically in the forward driving position D of the travel range selector lever 8 by the servo adjusting device 10 . This Stellein device comprises actuators 11 a, 11 b and 12, of which the actuators 11a and 11b for rotating the shift rod 7 are formed, thereby performing the actual engagement of the gears, while the existing of two series-connected actuating piston actuator 12 to select the individual gear pairs by longitudinal displacement of the shift rod 7 is determined. Gear selection and gearshifting are therefore carried out by separate actuators, which adjust the shift rod 7 in mutually independent directions, namely in the longitudinal direction and in the circumferential direction.

The actuators 11 a, 11 b and 12 are constructed in principle in the same way and are designed here as working with excess pressure. The actuators 11 a and 11 b correspond perfectly and each have a piston 43 or 47 , which is adjustable in a cylindrical housing and is provided with a membrane 44 or 48 , and which is loaded by a return spring 45 or 49 . The two pistons 43 and 47 are respectively disposed at the two ends of a piston rod 41 having mutually opposite direction of action, wherein the piston rod arms turn in Wesent union perpendicular to the shift rod 7 and on this by means of a lever 42 is arranged attacking. By pressurizing one of the actuators 11 a and 11 b associated pressurizing spaces 46 and 50 , the corresponding piston 43 and 47 and thus the piston rod 41 is adjusted, whereby the shift rod 7 is rotated. During this rotation of the shift rod 7 , the associated gear is then engaged by shifting the shift fork into which the shift finger 35 engages.

If both pressurization chambers 46 and 50 of the actuators 11 a and 11 b are ventilated, then the shift rod 7 is held in the middle or neutral gear position by the action of the return springs 45 and 49 , or the shift rod is loaded for adjustment in this position. An adjustment of the shift forks 37 to 39 in this idle position can, however, only take place with a previously engaged transmission gear if the self-retention of the sliding sleeves assigned to the gear wheel is overcome by reducing the engine pulling torque. The intermeshing teeth of the sliding sleeves and the gear wheels should namely be designed according to the invention so that they are automatically held in the engaged position in the presence of a minimum pulling torque exerted by the drive motor. This can be achieved by appropriately designing the flanks of the engagement teeth on the sliding sleeves or the driving teeth on the gear wheels, which for this purpose have at least on their pulling side such an undercut angle that a sliding sleeve engaging force component is generated when a predetermined minimum pulling torque is present which counteracts a restoring force applied here by the restoring springs 45 and 49 , respectively.

An example of the formation of such a toothing engagement is schematically indicated in a plan view of the toothing in FIG. 3. 64 a sliding sleeve and 65 the toothing assigned to this sliding sleeve should be indicated, while 66 represents a gear wheel and 67 the driving toothing associated with this gear wheel. The arrow 72 indicates the direction of torque transmission during train operation, in which the drive motor drives the vehicle wheels, while the opposite direction of transmission would drive the rolling wheels of the motor. It can now be seen from the illustration that in the engagement area of the toothings 65 and 67 the flanks 68 and 69, which abut one another during pulling operation, have an undercut angle α. This undercut angle α should be so large that above a certain minimum torque a frictional holding force is set, which holds the sliding sleeve 64 against the force acting on it in the direction of arrow 73 .

Such an undercut angle could also be provided on the thrust flanks 70 and 71 of the sliding sleeve toothing 65 and the driving toothing 67 of the gear gear 66 . However, it would be advantageous if no undercut angle is provided on these thrust flanks 70 and 71 , as is indicated in the drawing. The absence of an undercut angle on the thrust flanks of the engagement teeth prevents the sliding sleeve 64 from holding itself even in overrun mode, in which the gears should generally disengage automatically.

The effect of the formation of an undercut angle according to the invention, at least on the traction flanks of the engagement teeth 65 , 67 , is that when a sufficiently high engine pull torque is present, the gear once engaged remains engaged, but that when the pulling torque drops below a predetermined minimum value or when switching over Thrust operation due to the disengaging force 73 acting on the sliding sleeve 65, the gear is automatically disengaged.

Will call this releasing force, the processing in one embodiment of a Servostelleinrich shown in FIG. 2 by the return springs 45 or 49 hervorge, either continuously or in accordance with may now be an even better solution, only approximately in the region of lower Motorzugmomente near the Mindestzugmomentes on the sliding sleeve 64 come into effect. For this purpose, the actuation of the actuators 11 a and 11 b of the servo actuator 10 could be carried out so that the pressurization of the two actuators when engaging the assigned gear initially follows only for a short period of time, which is sufficient to ensure that the engagement gears engage securely bring to. Subsequently, the pressurization can be switched off for a short time in order to determine on the basis of the measuring transducers 23 and 24 which detect the transmission input and the transmission output speed whether the desired transmission gear is actually engaged. If the gear had not yet been engaged, the control unit 5 would first initiate a new gear engagement process. Thereafter, the relevant actuator can be pressurized again in order to now cancel the disengagement force exerted by the associated return spring 45 or 49 , so that the shift fork 37 , 38 or 39 actuated by the shift finger 35 in this gear is not constantly in contact with the Gearbox input shaft with rotating sliding sleeve 64 abuts under friction. Only in the vicinity of the minimum pulling torque, at which the gear should disengage automatically, the pressurization of the actuator is switched off completely, so that the release force exerted by the return spring on the sliding sleeve comes into effect fully and disengages when the minimum pulling torque is undershot the Mitnahmver toothing 67 of the gear 66 brings. The final shutdown of the pressurization of the actuator can be controlled depending on the position of the accelerator pedal or in some other way, in each case depending on the engine pulling torque, in such a way that this shutdown takes place at a second limit value, which in any case is above of the minimum pulling torque provided for the automatic disengagement of the gear.

Such a constant pressurization of the actuator 11 a or 11 b assigned to the respective gear is at least unnecessary if a spring exerting the restoring force would engage directly on the sliding sleeve 64 . In this case there would be no constant friction between the sliding sleeve and the associated shift fork, which usually engages in a recess on its outer circumference.

It turns out that with a switching device according to the invention downshifting from the individual transmission gears into the transmission idle not by servo actuation, but always automatically occurs exactly when the specified minimum torque of the drive motors is undercut. When on wear prevention between Shift fork and sliding sleeve is dispensed with or if the sliding in the gear engagement position directly from a spring or the same is loaded in the disengaging direction, the servo force to engage the respective transmission gears even for a short time, namely only until the final engagement of the gears and application sufficient engine torque.

The gear selection by axial displacement of the shift rod 7 takes place in the embodiment of the Servoschaltvorrich device 6 shown in the drawing with the help of the actuator 12 , which consists of a tandem cylinder. In this case, two pressurization spaces 53 and 56 , which are separated from one another in the tandem cylinder, are provided, to which pistons 51 and 54 provided with membranes 52 and 55 are assigned. While the second piston 54 is connected via a piston rod 60 directly to the shift rod 7 , the two pistons 51 and 54 are not rigidly connected to one another, but are separated at point 59 by a joint. The arrangement is now such that when the first pressurizing chamber 53 is pressurized, the shift rod 7 is only moved until the first piston 51 comes into contact with a stop formed as a transverse wall 57 . As a result, the shift finger 35 is adjusted from the starting position shown in the drawing, in which it is in engagement with the shift fork 37 in the shift gate assigned to the first and second gear, into the shift gate corresponding to the third and fourth gear, in which it is at the Shift fork 38 attacks. When the second pressurization chamber 56 of the actuator 12 is also acted upon, the second piston 54 is adjusted only until it abuts against the cylinder base 58 and the shift rod 7 is thereby shifted to engage the shift finger 35 in the shift gate of the shift fork 39 , which is assigned to the fifth forward gear.

A return of the shift rod 7 to the starting position is carried out by the return spring 9 after a corresponding shutdown of the pressurization of the rooms 56 and 53 , this shutdown in turn being controlled by the control unit 5 in accordance with the respective operating state of the vehicle.

It should also be mentioned here that to ensure engagement of only one gear by actuating only one shift fork by the shift finger 35, customary locking plates are provided.

The driver of a vehicle equipped with the automatic gearshift device according to the invention is essentially by operating the drive range selector lever 8, the three operating modes, namely D (forward), N (neutral) and R (reverse), available, in the neutral position N no gear and in the reverse gear position R after mechanical adjustment of the shift rod 7 by actuating the shift fork 40 by the shift finger 36 of the reverse gear. The start can be carried out by actuating a conventional friction clutch; However, it would be particularly favorable if an automatic starting clutch could be used.

A computer assigned to the control unit 5 determines in the operating position D of the driving range selector lever 8 from the engine speed, the driving speed and that based on the accelerator pedal position or a measurement value dependent thereon, such as, for. B. the intake manifold vacuum, he summarized the driver's desired torque, the cheapest gear, that is, the most favorable gear ratio for the respective operating state of the gear change transmission and then automatically performs the operations required for engaging the respective gear. For this purpose, the switching device 5 controls the electromagnetic pressure application valves 13 to 16 assigned to the servo control device 10 in such a way that the switching rod 7 carries out the adjustment movements required for gear selection and gear shifting.

To start the vehicle, the range selector lever 8 is first placed in the D range or when reversing in the R range. When arranging a conventional start-up clutch which can be actuated by a foot pedal, it must be ensured that the first transmission gear is engaged only after the clutch pedal has been depressed by appropriately acting on the servo control device 10 performing the gear shift. The start can then take place as usual with the help of the clutch pedal and by depressing the accelerator pedal. When a predetermined target engine speed is reached, which is, however, dependent on the torque request of the driver determined on the basis of the accelerator pedal position or the intake manifold vacuum, upshifting is then initiated in each case in the next higher gear.

When shifting gears themselves, for example by reducing the gas or by influencing the control unit 5 on actuators (not shown further here), the engine torque during the driving of the vehicle must be reduced to such an extent that it drops below the minimum torque, so that the gear engaged in each case automatically can disengage the way described above. At the same time or after the reduction in the engine torque and the disengagement of the old gear, the control unit 5 controls, depending on the shift direction, either a device for braking (when shifting up into higher gears) or for accelerating (when shifting down into lower gears) the drive motor 1 . If the engine speed corresponds to the target engine speed assigned to the new, next higher or next lower gear, which is determined taking into account the gear ratio jump and the driving speed of the vehicle, the gearshift device 6 is actuated to automatically switch on the corresponding next gear, in which the or the each selected gear responsible actuators 11 a or 11 b and 12 are pressurized. At the latest after switching on this gear, which takes place during the synchronous operation of the coupling members to be engaged, the engine torque and the acceleration of the engine are steadily increased again. Because of the switching on of the gears in the synchronous point, no synchronizing means are required on the coupling members, so that a simplification of the manual transmission occurs.

While the transmission gears can be disengaged when shifting even without a corresponding actuation of the accelerator pedal, solely by controlling the engine pulling torque from the control unit 5 , each time the accelerator pedal is released, there is automatically a freewheeling operation, i.e. disengagement of the gear transmission engaged and operation in Gearbox neutral position, since when the engine pulling torque required for the self-locking of the sliding sleeves is not reached, the currently engaged gear is disengaged automatically. The vehicle then continues to coast until the accelerator pedal is pressed again. Depending on the driving speed then present and, for example, also the actuation speed of the accelerator pedal, the appropriate gear for a new gear shift is selected and engaged by actuating the assigned actuators of the gear shifting device 6 . Such a freewheeling operation is characterized by the elimination of the engine braking effect and the engine running at engine idling speed due to reduced fuel consumption and lower pollutant values, so that the overall fuel consumption of the vehicle when using the gear shifting device according to the invention phases can be significantly reduced because of the relatively frequently occurring overrun operation.

However, it can also make sense to provide a way to switch off this freewheeling operation. For example, the automatic disengagement of the individual transmission gears when accelerator pedal release could be interrupted expediently whenever the vehicle is used on mountainous routes where engine braking in overrun is to be used to relieve the driving brakes. The freewheel shutdown could be brought about either by actuating a corresponding manual switch or also automatically by monitoring the inclination of the vehicle or the brake cylinder temperatures by means of appropriate sensors. Such a freewheel shutdown could be realized in that in such cases the disengaging force exerting on the sliding sleeves means such. B. the return springs 45 and 49 , can be suppressed by applying opposing forces even in the area of low engine torque. In the simplest case, the actuators 11 a or 11 b assigned to the respective transmission gears then remain constantly under pressure, at least until a new transmission gear selected by the control unit 5 is to be engaged.

Instead of or in addition to this freewheel cutoff, the control unit 5 could also cause the gearbox to be downshifted to the next lower gear.

Claims (15)

1.Device for the automatic switching of a multi-speed gear change transmission for vehicles, in particular motor vehicles, connected downstream of a drive motor, depending on the characteristics characterizing the operating state of the vehicle, with the individual transmission gears assigned, each consisting of a loose and a fixed gear pair and with one from a control unit-controlled servo device for moving from the idler gears of the gear pairs associated coupling members that produce a positive connection of the idler gear assigned to the respective gear with an on or drive shaft of the transmission, the coupling members ( 64 , 66 ) for self-holding in the engaged position when a value above a minimum value is present, the tensile torque of the drive motor ( 1 ) and for automatic disengagement when the minimum tensile torque is undershot are formed, characterized in that ß the coupling members are formed with engagement teeth ( 65 ) ver sliding sleeves ( 64 ) are formed, each with on the idler gears ( 66 ) provided driving teeth ( 67 ) can be brought into a handle, and that at least the other flanks adjacent to each other during train operation ( 68 , 69 ) of the toothings ( 65 , 67 ) have such an undercut angle that during the application of a tensile torque of the drive motor ( 1 ) above a minimum value, the toothing engaging holding forces are generated, and that means for applying a to the sliding sleeves ( 64 ) at least temporarily, continuously acting disengagement forces are provided, which automatically disengage the gears when the minimum tensile torque is undershot. 2. Device according to claim 1, characterized in that the disengagement force is applied to the sliding sleeves ( 64 ) essentially only in the area of low tensile torques of the drive motor ( 1 ). 3. Device according to claim 1, characterized in that the thrust flanks ( 70 , 71 ) of the engagement teeth ( 65 ) of the sliding sleeves ( 64 ) and the driving teeth ( 67 ) of the idler gears ( 66 ) are undercut freely. 4. Device according to claim 1, characterized in that the means for applying the disengagement force are formed by return springs ( 45 , 49 ). 5. Device according to claim 4, characterized in that the return springs act directly on the sliding sleeves ( 64 ). 6. A device according to claim 4, characterized in that the restoring springs (45, 49) are integrated in the servo actuator (10) and via the switching movements of the Servorstelleinrichtung (10) on the sliding sleeves (64) transmitting actuators (41, 7, 35 , 37 to 39 ) on the sliding sleeves. 7. Device according to one of claims 1 to 6, characterized in that the servo control device ( 10 ) is effective at least for a predetermined time during the engagement of the respective transmission gears for actuating the sliding sleeves ( 64 ) in the engagement direction. 8. Device according to claim 7, characterized in that the actuation of the sliding sleeves ( 65 ) by the servo adjusting device ( 10 ) can be switched off again after a predetermined time after the arrival of the engagement signal. 9. Device according to claim 8, characterized in that the actuation of the sliding sleeves ( 65 ) by the servo-adjusting device ( 10 ) after their switching off to compensate for the spring force acting in the release direction of the return springs ( 45 , 49 ) can be switched on again and only then in the Proximity of the minimum pulling torque causing the automatic displacement of the sliding sleeves ( 64 ) can be switched off again. 10. The device according to claim 9, characterized in that the actuation of the sliding sleeves ( 64 ) by the servo adjusting device ( 10 ) when falling below the above the automatic disengagement of the sliding sleeves causing minimum pulling torque limit value can be switched off. 11. Device according to one of claims 1 to 10, characterized in that the servo adjusting device ( 10 ) is designed to adjust a shift rod ( 7 ) actuating the sliding sleeves in two mutually independent directions. 12. The device according to claim 11, characterized in that the servo adjusting device ( 10 ) has two mutually opposite direction of action on a piston rod ( 41 ) engaging actuators ( 11 a, 11 b), and that the piston rod transverse to the longitudinal direction of the shift rod ( 7 ) arranged and connected to this to form a lever arm ( 42 ). 13. The device according to claim 12, characterized in that the actuators ( 11 a, 11 b) each have a pneumatically actuated actuating piston ( 43 , 47 ) against a return spring ( 45 , 49 ). 14. Device according to claim 11 to 13, characterized in that the servo adjusting device ( 10 ) has a longitudinally on the shift rod ( 7 ) engaging, adjustable in several stages further actuator ( 12 ). 15. The device according to claim 14, characterized in that the further actuator ( 12 ) has two separate, pneumatically actuated actuating pistons ( 51 , 53 ) which are provided one behind the other with different adjustment paths.