DE29802183U1 - Control device for an automatic transmission of a commercial vehicle - Google Patents

Abstract

The gearbox is operated by an electronic control unit (1). The automatic gear unit (2) has a clutch (3) which is engaged and disengaged by a hydraulic control (4). The gearbox (5) has a gear-change unit (6) which may be hydraulic or pneumatic, and which engages and disengages different cogs as required. The gears may have e.g. 16 forward gears and two reverse gears. The electronic control unit (1) consists primarily of a proportionate magnetic valve (7) operating the clutch hydraulic control, a set of valves (8) controlling the gear change unit, a gear selection lever (9) in the vehicle cabin, and a microprocessor control unit (10). The microprocessor generates the signals necessary for operation of the magnetic valve and the valves, in response to input signals.

Description

TER MEER - MÜLLER - STEINMEISTER & PARTNERS

PATENT ATTORNEYS - EUROPEAN PATENT ATTORNEYS

Dr. Nicolaus ter Meer, Dipl.-Chem. Helmut Steinmeister, Dipl.-Ing.

Frithjof E. Müller, Dipl.-Ing. Manfred Wiebusch

Peter Urner, Dipl.-Phys. ·

Mauerkircherstrasse 45 Artur-Ladebeck-Strasse 51.

D-8000 MUNICH 80 D-4800 BIELEFELD 1

_st/za >> 06.02.1998

IVECO FIAT S.p.A.

Via Puglia 35 1-10156 Turin

CONTROL DEVICE FOR AN AUTOMATIC TRANSMISSION OF A COMMERCIAL VEHICLE

Priority: 11.02.1997 / Italy / TO97 A 000108 (P)

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CONTROL DEVICE FOR AN AUTOMATIC TRANSMISSION A COMMERCIAL VEHICLE

The present invention relates to a control device for an automatic transmission of a commercial vehicle, in particular for an automatic transmission with manual transmission or gear transmission.

In order to improve the driving conditions of vehicles, in particular commercial vehicles whose operating conditions are relatively complex, vehicle manufacturers are striving to automate certain functions, including the gearshift function.

In known automatic transmissions, an electronic unit is provided which controls the engagement of the gears in accordance with input signals emanating from the gearshift lever. This lever can generally be moved linearly from a central rest position in two opposite directions, corresponding to the first gear above or below the currently engaged gear, or in four control positions of two positions each on either side of the central position, which enable the engagement of the first or second gear above the central position or the first or second gear below the central position.

These transmissions have been further developed by adding devices that provide rapid and automatic gear shifting that best matches the machine characteristics to the driver's desired driving style. These devices can typically be selected by buttons and/or switches on the gearshift handle.

The automatic selection of the optimum gear not only improves the efficiency of the machine, but also makes driving easier by reducing the amount of thought required when changing gears. This allows the driver to concentrate more on driving the vehicle. The automatic selection also makes it possible to react quickly to emergency situations without the risk of error, thus providing safety benefits.

The advantages of using an automatic gear selection system

instead of manual gear shifting are partially offset by the need to operate the relevant button (or switch) at the same time as operating the gear lever. This operation can indeed distract the driver's attention and lead to driving errors, especially in emergency situations.

The object of the invention is to create a control device for an automatic transmission of a commercial vehicle, which makes it possible to carry out gear changing processes automatically in such a way that the disadvantages mentioned above are overcome.

According to the invention, a control device for an automatic transmission of a commercial vehicle with a manual or gear transmission, which is provided with a fluid actuating device for switching the gears on and off, comprises the following elements:

- Valves to control the switching unit,

- a microprocessor control unit which generates control signals at least for the valves in accordance with input signals,

- a gear lever which can be manually operated by the driver and is straight movable in one plane and can be moved into four different control positions from a central rest position, with a first and second position on one side of the rest position and a third and fourth position on the opposite side of the rest position, the second and fourth positions being at a greater distance from the rest position than the first and third positions,

- a first set of sensors in connection with the manual transmission, which provide a first set of input signals to the control unit, which are representative of the respective gear position of the manual transmission,.

- a second set of sensors connected to the control unit, providing a second input signal representative of the speed of the vehicle,

- a switching device in connection with the gear lever which supplies to the control unit a third set of input signals corresponding to the manual movement of the gear lever to one of the positions,

- an auxiliary selection device F on the gear lever, which can be operated manually in connection with the lever and is able to deliver a fourth input signal to the control unit, characterized in thatJ3 the

signal to the control unit, characterized in that the control unit comprises:

- a first means for determining the gear to be engaged, operable in the presence of the fourth input signal indicating that the button F is not operated and producing a gear control signal (r _cmax i,r _cmax 2· ■~ ^r n(maxl)' ^r n(max2)' which have been automatically calculated on the basis of predetermined logic steps corresponding to at least the second and third input signals and

- a second device for determining the gear to be engaged, which is operable in the presence of a fourth input signal indicating that

the button F is pressed and is capable of generating a control signal in accordance with at least the first signal for changing the engaged gear in the upward or downward direction by a predetermined number of steps.
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In the following, preferred embodiments of the invention are explained in more detail with reference to the accompanying drawings.

- Fig. 1 is a schematic representation of a control device according to the invention for an automatic transmission;

- Fig. 2 is a side view of a control lever of the device according to Fig. 1;

- Fig. 3 is a front view of the shift lever of Fig. 2;

- Fig. 4 is a block diagram illustrating the operation of the control device according to the invention as shown in Fig. 1.

Fig. 1 shows with the reference number l· a control device for an automatic transmission 2 of a commercial vehicle.

The automatic transmission 2 comprises a clutch 3 controlled by a hydraulic actuator 4 which determines engagement and disengagement of the clutch, and a manual transmission 5 with a shift unit 6 which may be hydraulic or pneumatic and is capable of engaging and disengaging various transmission gears. The manual transmission 5 may, for example, have 16 forward gears and two reverse gears.

The control device 1 essentially comprises a proportional solenoid

valve 7 which controls the actuator 4 of the clutch 3, a set of valves -8 which control the switching unit 6 of the gearbox, a gear lever 9 which can be housed inside the driver's cabin of the vehicle and is manually operated by the driver, and a microprocessor control unit 10 which generates control signals 1,1,12 for the solenoid valve 7 and the valves 8 in accordance with the input signals, as will be explained below.

In particular, the control unit 10 is connected to a position transducer 13, which is associated with the actuator 4 of the clutch 3 and sends to the control unit 10 a signal 14 indicating the movement of the clutch. For this purpose, a number of sensors 15 are provided, which are associated with the moving components of the switching unit 6 and send signals 16 corresponding to the gear stage engaged. Furthermore, a selector device is provided, which is associated with the gear lever 9 and sends to the unit 10 signals 18a, 18b, 18c, 18d corresponding to the manual movements of the lever.

The gearshift lever 9 (Figs. 2 and 3) is movable in a plane a extending in the longitudinal direction of the vehicle and can be switched from a central rest position, designated O in Fig. 2, to four different control positions. Two of the positions lie in the forward direction of the vehicle with respect to position O and are usually designated by the letters U ("up") and EU (Extra-UP) according to their distance from position O. The other two positions lie in the opposite direction of the vehicle with respect to position O and are usually designated by the letters D ("down") and ED (Extra-down) according to their distance from position O.

The gear lever 9 consists of a shaft 19 pivotally mounted on a base 20 which can be secured to the vehicle. A handle 21 is located at the free end of the shaft 19. The previously mentioned selection device consists of a number of switches 22 of conventional type, not shown in detail, located inside the base 20 and operable by the gear lever 9 and delivering corresponding signals 18a to the unit 10 when the gear lever is moved to one of the control positions U, EU, D and ED described above. This selection device further comprises two buttons

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on the sides of the handle 21, designated by the letters F and N, and a collar R, which is coaxially surrounded by a rod 19 and on which it can slide between a lower rest position, in which it is held elastically by means not shown, and an upper actuating position ;. The buttons F and N and the collar R actuate switches, not shown, which are connected to the control unit 10. These switches make it possible to send to the control unit 10 the signals 18b, 18c, 18d, which indicate whether the corresponding buttons or the collar have been actuated.

The control unit 10 further comprises an input signal 23 which is proportional to the speed of the vehicle and is emitted by known sensors 24, which consist, for example, of a speed or rotational speed sensor on the drive shaft of the gearbox 5.

The operation of the control unit 1 will be explained below with reference to the block diagram of Fig. 4, which shows the sequence of operations cyclically performed by the control unit 10, as well as the operations concerning the gearbox 5. The control of the clutch 3 is carried out in a conventional manner and will therefore not be explained in detail.

For simplicity and brevity, in cases where the control unit 10 performs an operation based on an input signal corresponding to a manual operation, the check of the state or value of the signal is replaced in the key of the block diagram by a sign for the relevant operation and is thus described below. For example, if the unit 10 checks whether the signal 18a corresponding to the operation of the gear lever 9 is active in one of the control positions, it is only checked by the unit 10 whether the lever has been moved to that position. It is thus obvious that the signal is being checked. Likewise, in cases where the unit 10 generates a signal capable of controlling an actuator which performs a certain operation, the result of the operation (for example the engagement of a certain gear ratio) is indicated in the block diagram instead of the activation of the corresponding signal.

According to the diagram in Fig. 4, the cycle begins in a block 25.

In a subsequent step 26, the unit 10 checks whether the button N on the gear lever 9 has been pressed. If this has happened, the program proceeds to step 27, where the neutral position of the gearbox 5 is commanded. The program then moves to step 28, where it is checked whether the gear is disengaged, and if so, the cycle ends.

If, on the other hand, button N has not been pressed, the program moves from step 26 to step 29, where unit 10 checks whether the vehicle speed is below a very low predetermined threshold of, for example, 2 km/h, i.e. whether the vehicle is almost stationary.

If this is the case, the program moves to step 30 where a termination program is executed, the operating steps of which, for example, follow a control logic of a known type, similar to that described in Italian Patent No. 1257945.

If the vehicle is not stationary, ie if the vehicle is running, the program moves to step 31 where a counter k, the function of which will be explained later, is set to 0. From block 31 the program goes to block 32 where unit 10 checks whether the gear lever has been moved to position U. If this is the case, it is checked in step 33 whether the value of counter k is equal to a predetermined maximum value k _max . If this is not the case, a subsequent step 34 increases the value of the counter k by one unit and the program goes back to step 32. When the value of the counter k reaches the value k _max , i.e. when the shift lever 9 is held in the U position for a predetermined period of time, the program goes on to step 35. In practice, steps 32,33,34 together form a waiting station 41 which is necessary to clarify whether the shift lever 9 has been pushed completely into the U position or that the position has only been reached temporarily for a very short time while the lever continues to move to the EU position. In the latter case, the U command must therefore be ignored by the control unit.

At step 35, it is checked whether button F has been pressed. If this is the case, the program goes to step 38, where the control unit

checks whether the gearbox is in neutral. If the gearbox is not in neutral but in a forward gear (r), the program goes to step 39 where it is checked whether the next higher gear (r + 1) above the currently engaged gear is possible, i.e. whether, in terms of vehicle speed, this new gear is at an engine speed higher than the minimum speed at which standstill is prevented. If the new gear is not permitted, the request is ignored and the end of the cycle is reached. If, on the other hand, the new gear is permitted, the program moves to step 40 where the intervention is commanded and then to step 43 where it is checked on the basis of the value of signal 16 whether the gear is engaged. If this is the case, the end of the cycle is reached. If this is not the case, the program moves back to step 43, which therefore forms a waiting step and checks whether the preselected gear has been engaged.

If button F has not been depressed at step 35 and if the neutral gear position has been determined at step 38, the program goes to step 36 where, on the basis of signal 23 and the gear ratio of the various gears, the gear r is calculated which gives an engine speed corresponding to a first predetermined maximum torque value. The program then moves to step 37 where a gear engagement is ordered and finally to the wait and test step 43.

If the shift lever 9 has not been moved to the U position or has not been held there for a sufficient time, the program moves from step 32 to step 44, where it is checked whether the shift lever has reached the EU position.

If this is the case, step 45 checks whether button F has been pressed. If this is the case, step 46 checks whether the gearbox is in neutral. If it is not in neutral but in a forward gear R, step 47 checks whether the second gear above the gear currently engaged can be engaged in the sense mentioned above. If the new gear is possible, step 48 instructs the intervention, and finally step 43 waits and checks whether the gearbox is in neutral.

gear is engaged. If, on the other hand, the required gear is not possible, the program moves to step 39 as described above.

From step 45, if button F has not been depressed, and from step 46, if the neutral gear position has been confirmed, the program goes to step 36a, where, on the basis of the signal 23 and the gear ratio of the various gears, the gear r is calculated which gives an engine speed corresponding to a second predetermined maximum available torque value; then the program goes to step 37a, where this gear is engaged, and finally to step 43 to wait and confirm that the gear is engaged.

If the lever has not been moved to the EU position, the program moves from step 44 to step 50, where the unit 10 checks whether the gear lever has been moved to position D. If this is the case, a check is made at 54 to see whether the value of the counter k is equal to a predetermined maximum value k _max . If this is not the case, the value of the counter k is increased by one unit at step 55 and the program goes back to step 50. If the value of the counter k reaches the maximum value k _max , i.e. if the gear lever 9 has been held in position D for a predetermined time, the program goes to step 56. In practice, steps 50, 54 and 55 together form a wait step 59 (as does wait step 41) where it is decided whether the gear lever 9 has been deliberately moved to position D or whether this position has only been reached temporarily for a short time while the lever has been pushed to position ED. In the latter case, the D signal must be ignored by unit 10.

At 56 it is checked whether the button F has been pressed. If this is not the case, at 57 the gear r _n r _max ]j corresponding to the engine speed (n(maxl)) is calculated on the basis of the signal 23 and the gear ratio of the various gears, which is close to the maximum obtainable angular velocity (n(Pmax)), for example 70 and 90 % of n(Pmax), and then the engagement of the gear is instructed at 58.
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When step 43 is reached, the system waits and checks whether the gear has been engaged. ^e

When button F has been pressed, the program moves from step 56 to step 60, where unit 10 checks whether the gearbox is in neutral. If this is the case, the program goes to step 57 and proceeds as described above. If, on the other hand, the gearbox is not in neutral but a forward gear is engaged, a step 64 is reached where it is checked whether the gear below the currently engaged gear is possible, i.e. whether, taking into account the vehicle speed, this new gear would lead to an engine speed below a predetermined limit, for example n(maxl), in order to prevent the engine from over-revving. If the new gear is not possible, the request is ignored and the cycle is terminated. If, on the other hand, the new gear is possible, the program moves to step 65 which commands engagement of the gear and then to step 43 to wait and check that the gear is actually engaged.

If the shift lever 9 has not reached position D and is not held there long enough, the program moves from step 50 to step 67. There it is checked whether the shift lever has reached position ED.

If this is the case, a check is made at 68 to see whether button F has been pressed. If necessary, a check is made at step 69 to see whether the gearbox is in the neutral position. If the answer is negative, i.e. if a forward gear is engaged, a check is made at 70 to see whether the second gear below the one engaged in the sense mentioned above is possible with respect to the threshold value n(maxl).

If the new gear is possible, then at step 71, its engagement is commanded, and at step 43, it waits and checks whether the gear is engaged. If, on the other hand, the requested gear is not possible, the program moves to step 64, where the possibility of a downshift by one step is checked.

From step 68, if the button F has not been depressed and from step 69, if the neutral gear position has been confirmed, step 73 is reached, where on the basis of the vehicle speed and

of the gearbox ratios, the gear is calculated that corresponds to an angular speed close to the limit of the mechanical strength of the machine itself or the clutch ("maximum rpm"), which must only be reached in exceptional situations and absolute emergencies. This value can be, for example, equal to n(max2) = 115% of n(Pmax).

A step 54 is then reached in which the engagement of this gear is instructed and then at step 43 it is waited and checked whether the 1Q gear is engaged.

In functional terms, the operation of the control device can be summarized as follows:

If the gear lever is moved to position U without pressing button F, or if button F is pressed but starting from a neutral position, the engagement of the gear corresponding to a first maximum torque is commanded. On the other hand, if the gear lever is moved to position U while button F is pressed and under normal running conditions (manual transmission not in neutral), unit 10 commands the engagement of the gear above the currently engaged gear, or the command is ignored if that gear is not possible.

On the other hand, if the driver moves the lever to the EU position without pressing button F, or if button F is pressed but starting from the neutral position, the gear corresponding to a second maximum torque is engaged.

However, if the gear lever is moved to the EU position while button F is depressed and under normal running conditions, the second gear above the currently engaged gear is engaged if possible, or the next higher gear if possible. If the gear lever is moved to position D without depressing button F, or if button F is depressed but starting from the neutral position, the lowest possible gear is instructed to be engaged, i.e. a gear compatible with a

maximum speed limit under normal conditions (maximum power conditions). On the other hand, when position D is on under normal running conditions and when button F is pressed simultaneously,

•' has been pressed, the unit IO gives instructions ^: to engage the gear below the currently engaged gear, or it ignores this instruction if it is not feasible.

If the driver moves the lever to the EU position without pressing button F, or if the gear is shifted from neutral with button F pressed, an emergency situation is present and the lowest gear compatible with the mechanical integrity of the machine and/or the clutch (maximum engine speed) is engaged. On the other hand, if the gear lever is in the EU position with button F pressed under normal running conditions, the second gear up is engaged, if possible in relation to the normal operating range of the machine, or the next higher gear if possible.

In practice, the driver need only move the lever to the U or EU position if he wants to have maximum torque conditions and drive economically and slowly, to the D position if he wants to have acceleration and essentially maximum power and drive quickly, or to the ED position which, as mentioned, represents an emergency situation to obtain maximum acceleration. The same conditions are achieved by moving the lever with the F button depressed when starting from the neutral position. On the other hand, under normal driving conditions, if U or EU is switched on and the F button is pressed, a single or even double upshift occurs, while actuation of the D or ED control results in a single or double downshift. The characteristics of the control device 1 according to the present invention should be obvious.

In particular, the gearshift logic gives priority to the execution of automatic functions, making driving the vehicle less tiring and also safer and more economical. The driver, however, has the option of selecting gears manually by pressing button F while operating the gear lever, using simple and intuitive commands.

' The control device allowing a single or multiple gear change prevents the erroneous or accidental engagement of gears which are incompatible with proper operation or which could lead to damage to the machine unit or constitute a risk to operational safety.

The automatic control, which ignores incorrect or faulty commands, and the simplicity of the manual controls ensure correct and safe driving and that the switching functions can be learned quickly.

Claims (6)

- 13 - PROTECTION CLAIMS 1. Control device for an automatic transmission (2) of a commercial vehicle with a manual transmission (5) which is equipped with a fluid-operated switching unit (6) which controls the engagement and disengagement of the gears, with - Valves (8) for controlling the switching unit (6), - a microprocessor control unit (10) which generates control signals (12) at least for the valves (8) in accordance with input signals (18a, 18b, 18c, 18d), - a gearshift lever (9) which can be manually operated by the driver and is movable in a straight line in a plane (a) and can be moved into four different control positions (U,EU ₁ D,ED) from a central rest position (O), a first and second position (U ₁ EU) being on one side of the rest position (O) and a third and fourth position being on the opposite side of the rest position (O), and the second and fourth positions (EU.ED) being at a greater distance from the rest position (A) than the first and third positions (U ₁ D), - a first set of sensors (15) in connection with the manual transmission, which provide a first set of input signals (16) to the control unit, which are representative of the respective gear position of the manual transmission, - a second set of sensors (24) in connection with the control unit, which provides a second input signal (23) representative of the speed of the vehicle, - a switching device (22) in connection with the gear lever (9) which delivers to the control unit (10) a third set of input signals (18a) corresponding to the manual movement of the gear lever (9) into one of the positions (U ₁ EU ₁ D ₁ ED), - an auxiliary selection device (F) on the shift lever (9) which can be operated manually in conjunction with the lever (9) and is capable of delivering a fourth input signal (18b) to the control unit (10), characterized in that the control unit (10) comprises: - a first device for determining the gear to be engaged (36,37,36a,37a, 57,58,73,74), which is operable in the presence of the fourth input signal (18b) indicating that the button (F) is not actuated and generates a gear control signal (12) ( ^r cmaxl ^>r cmax2' ^r n(maxl)' ^r n(max2)', which have been automatically calculated on the basis of predetermined logical steps corresponding to at least the second (23) and third (18a) input signals and
- a second device for determining the gear to be engaged (39,40,47,48,64,65,70,71), which is operable in the presence of a fourth input signal (18b) indicating that the button (F) is actuated, and is capable of generating a control signal (12) in accordance with at least the first signal (16) for changing the engaged gear in an upward or downward direction by a predetermined number of steps. 2. Device according to claim 1, characterized in that the second Device for determining the gear to be engaged (39,40,47,48,64,65,70,71) a device (40,48,65,71) for deciding for one or two gear shifts upwards or one or two gear shifts downwards in relation to the respective engaged gear according to the 15 manual movement of the gear lever (9) into the first (U), second (EU), third (D) or fourth (ED) position. 3. Device according to claim 1 or 2, characterized in that the means (38,46,60,69) for actuating the first device for determining the gear to be engaged (36,37,36a,37a, 57,58,73,74) in the presence of the first input signal (16) indicating the neutral position of the gearbox. 4. Device according to one of the preceding claims, characterized in that the first device for determining the gear to be engaged (36,37,36a,37a,57,58,73,74) comprises: - a first control device (37) for generating a signal (12) corresponding to the third input signal (18a) based on the manual
Movement of the shift lever (9) to the first position (U),
which signal (12) to engage a first gear
(r _nmax j) which has been calculated according to a
Speed of the machine at which a first specified torque value
is delivered, - a second control device (37a) which, in accordance with the third
input signal (18a) corresponding to the manual movement of the gear lever (9) to the second position (EU), a signal (12)
for the engagement of a second gear (r _nmax 2), which is the machine speed at which a second predetermined torque value is delivered, - third control means (58) for generating, in accordance with a third input signal (18a) resulting from the manual movement of the gear lever (9) to the third position (D), a signal (12) for engaging a calculated third gear (r _n ( _max i)) corresponding to an engine speed which is at least close to a speed at which the maximum power is delivered, - a fourth control device (74) capable of generating, in response to a third input signal (18a) resulting from the manual movement of the gear lever to the fourth position (ED), a signal (12) for the engagement of a fourth calculated gear (r _n r _max 2)) corresponding to the maximum engine speed permitted by the mechanical strength of the engine and the transmission. 5. Device according to claim 4, characterized in that the first device for determining the gear to be engaged (36,37,36a,37a,57, 58,73,74) comprises first (36), second (36a), third (57) and fourth (73) computing devices which are associated with the first (37), second (37a), third (58) and fourth (74) control devices and which, on the basis of the gear ratios of the gears and the second signal (23), supply gear wheel numbers which correspond to the first (r _nmax i), second (r _nmax 2), third (r _n ( _maxl )) and fourth (r _n r _max 2j) calculated gear. 6. Device according to one of the preceding claims, characterized in that the means for manual gear selection (39,40; 47,48; 64,65; 70,71) comprise a device (39,47,64,70) which prevents the engagement of a desired gear if the engine speed corresponding to this gear is not within a normal operating range of the machine itself.