DE102005028551B4 - Control device and method for an automatic transmission - Google Patents

Abstract

Control device for an automatic transmission of a motor vehicle with- a target gear determination device (21) and- a gearshift implementation device (22), wherein - the target gear determination device (21) determines a gear to be engaged, - the gearshift implementation device (22) engages the gear to be engaged and - a gearshift sequence dependent thereon is whether the gear to be engaged deviates from an actual gear by one or more than one gear, with the target gear determining device (21) being provided for - determining a target gear, - determining a parameter (k) when the target gear changes, which indicates a measure of the probability of a further change in the target gear and- to determine the gear to be engaged as a function of the target gear and said parameter (k) and the target gear determining device (21) is also provided for this purpose,- if there is a low probability of a further one Change in the target gear indicating parameter (k) in the event of a change in the target gear, to immediately accept the changed target gear as the gear to be engaged and - if there is a parameter indicating a high probability of a further change in the target gear when there is a change in the target gear, not to immediately accept the changed target gear as the gear to be engaged to take over the course.

Description

The invention relates to a control device for an automatic transmission according to the preamble of claim 1 and a method for operating an automatic transmission of a motor vehicle according to the preamble of claim 11.

The DE 103 38 624 A1 and EP 1 117 951 B1 describe a control device of an automatic transmission of a motor vehicle with a target gear determination device and a gearshift implementation device. The setpoint gear determination device determines a gear to be engaged by the transmission as a function of operating parameters of the motor vehicle. This gear to be engaged is engaged by the shifting implementation device by actuating shifting elements of the transmission. The course of the shift depends on whether a single shift or a multiple shift is carried out. In the case of a single shift, the gear to be engaged deviates from an actual gear by only one gear, while in the case of a multiple shift, by more than one gear. The actual gear is the gear currently engaged in the transmission.

The multiple circuit is not just a series of single circuits. It is designed in such a way that gear shifting is quick and easy. In particular, multiple shifting is carried out in such a way that a rotational speed of the engine of the motor vehicle has an almost constant gradient during shifting. This leads to quick shifts and is perceived as comfortable by a vehicle driver.

However, it can happen that the setpoint gear determination device requests a single shift and shortly thereafter another single shift. If the shift execution device has already started the first shift, no more multiple shifts can be started. In this case, several individual circuits must be linked together.

In contrast, it is the object of the invention to propose a control device and a method by means of which shifts can be carried out quickly and conveniently. According to the invention, the object is achieved by a control device having the features of claim 1 and a method according to claim 11.

According to the invention, the target gear determination device is provided to determine a target gear. The desired gear is determined on the basis of stored rules as a function of operating variables of the motor vehicle, for example a vehicle speed and a power requirement signal. The target gear determination device DE 103 38 624 A1 takes over this target gear immediately as the gear to be engaged, so that when the target gear changes, a gearshift is immediately triggered by the gearshift implementation device.

When there is a change in the target gear, the target gear determining device determines a parameter which specifies a measure of the probability of a further change in the target gear. The parameter can be determined, for example, using the operating variables mentioned or changes therein.

After determining the parameter, the target gear determining device determines the gear to be engaged as a function of the target gear and the determined parameter. The target gear determining device can, for example, adopt the target gear immediately or with a delay as the gear to be engaged.

The parameter thus represents a measure of the probability of whether a shift by one gear or by several gears will be carried out. By evaluating the parameter, the type of gearshift, ie single or multiple gearshifts, can be selected in such a way that there is a very high probability that the gearshift will take place quickly and conveniently.

In this way, the gearshift can be completed earlier and run particularly comfortably compared to an immediate transfer of the target gear as the gear to be engaged without taking the parameter into account.

The transmission can be designed, for example, as an automatic transmission with planetary gearsets, as an automated manual transmission, or as a continuously variable transmission with an operating mode in which fixed, predetermined gear ratios are set.

The advantages described are particularly evident during downshifts in the transmission.

In an embodiment of the invention, the target gear determination device is provided to determine the target gear as a function of a power demand signal and/or a speed signal. The parameter is determined as a function of a rate of change of the power requirement signal and/or the speed signal. The power request signal is in particular by the vehicle driver by means of a power actuator, esp special of an accelerator pedal. The driver of the vehicle thus requests power from the engine of the motor vehicle. The power demand signal can represent, for example, a position of an accelerator pedal, a position of a throttle valve, a fuel injection quantity or a target torque of the drive machine.

With the power request signal, the driver of the vehicle indicates his desire regarding the longitudinal dynamics of the motor vehicle. This signal will also be used to determine target gear. If the power demand signal rises, for example, the target gear can be reduced, ie a downshift can be triggered. If the power demand signal rises sharply, a multiple downshift can be triggered, for example. The rate of change of the power demand signal can be used to estimate whether the power demand signal will change only slightly or very greatly. For example, given a high rate of change in the power demand signal, the parameter indicates a high probability of a further change in the target gear. In contrast, the parameter indicates a low probability with a small rate of change.

The power demand signal can also be generated by a further control device of the motor vehicle, for example by a cruise control system.

The speed signal can be determined, for example, from measured speeds of wheels of the motor vehicle or from a speed at the output of the transmission. Taking into account the rate of change of the speed signal when determining the parameter is particularly advantageous when the motor vehicle brakes heavily. One or more gears can be skipped during the downshift that is then required. The downshift can then be carried out as a multiple shift.

In a refinement of the invention, the setpoint gear determination device is provided for the purpose of estimating a curve of the power requirement signal with the aid of the rate of change of the power requirement signal in order to determine the parameter. With this, the value of the power demand signal at a certain point in time can be estimated in advance. It can then be checked whether this estimated value would result in a further change in the setpoint gear. If this is the case, then the parameter indicates, for example, a high probability of a further change in the setpoint gear.

In an embodiment of the invention, the target gear determination device is provided for estimating a course of the speed signal with the aid of the rate of change of the speed signal in order to determine the parameter. This allows the value of the speed signal to be estimated in advance at a specific point in time.

In an embodiment of the invention, shifting lines are stored in the target gear determination device. The setpoint gear changes when an operating point of the motor vehicle that is dependent on the power requirement signal and/or the speed signal exceeds a shifting line. The operating point can, for example, reflect the position of the accelerator pedal and the speed of the motor vehicle. Such a determination of the target gear is generally known. For example, such an approach in the DE 195 11 866 A1 described in detail, the description of the determination of the target gear is hereby explicitly included in the disclosure of the present application.

• - welche eine hohe Wahrscheinlichkeit für eine weitere Änderung des Sollgangs anzeigt, wenn der vorausberechnete Arbeitspunkt eine weitere Schaltlinie überschreitet und
• - welche eine niedrige Wahrscheinlichkeit für eine weitere Änderung des Sollgangs anzeigt, wenn der vorausberechnete Arbeitspunkt keine weitere Schaltlinie überschreitet.

The target gear determination device is also provided to determine a parameter

• - Which indicates a high probability of a further change in the target gear if the pre-calculated operating point exceeds another shift line and
• - which indicates a low probability of a further change in the target gear if the pre-calculated operating point does not exceed any further shift line.

The setpoint gear determination device thus determines a probable or precalculated operating point and uses the stored shifting lines to check whether this operating point would lead to a further change in the setpoint gear. Depending on the result of the test, the setpoint gear determination device then determines the parameter.

• - bei Vorliegen einer eine niedrige Wahrscheinlichkeit für eine weitere Änderung des Sollgangs anzeigenden Kenngröße bei einer Änderung des Sollgangs den geänderten Sollgang sofort als einzulegenden Gang zu übernehmen und
• - bei Vorliegen einer eine hohe Wahrscheinlichkeit für eine weitere Änderung des Sollgangs anzeigenden Kenngröße bei einer Änderung des Sollgangs den geänderten Sollgang nicht sofort als einzulegenden Gang zu übernehmen.

In an embodiment of the invention, the target gear determination device is provided for

• - If there is a parameter indicating a low probability of a further change in the target gear when there is a change in the target gear, to immediately accept the changed target gear as the gear to be engaged and
• - If there is a parameter indicating a high probability of a further change in the target gear when there is a change in the target gear, not to immediately accept the changed target gear as the gear to be engaged.

If a parameter indicating a low probability is present, a single shift is thus immediately triggered.

On the other hand, if a parameter indicating a high degree of probability is present, the gearshift is not triggered immediately, but instead a wait is made to see whether the target gear changes again within an adjustable and storable time period. After the period of time has elapsed since the first change in the setpoint gear, the then current setpoint gear is adopted as the gear to be engaged. If the target gear has changed again, the shift is carried out as a multiple shift. The target gear can also change several times during the period of time, so that multiple shifts that skip more than one gear can also be triggered.

If a single shift had already been triggered with the first change in the desired gear, then the shift would have taken place as a series of single shifts in the event of a further change in the desired gear.

It is also possible for a new parameter to be determined if there is a further change in the target gear, and for a new parameter to be present that indicates a high degree of probability to start anew until the target gear is adopted as the gear to be engaged. If the new parameter indicates a low probability, the target gear is immediately adopted as the gear to be engaged.

Instead of adopting the target gear as the gear to be engaged after a period of time has elapsed, the target gear can also be adopted if the target gear changes again.

In an embodiment of the invention, the target gear determination device is provided to check a termination condition if a parameter indicating a high probability is present and to accept the changed target gear as the gear to be engaged if the termination condition is met or at the latest after the adjustable period of time has expired. A termination condition can be, for example, that the rate of change of the power demand signal has decreased by more than a definable value. A further termination condition could also be that, with the current rate of change of the power demand signal, no further shifting line could be exceeded before the expiry of the specified period of time.

This can prevent the shift from being unnecessarily delayed.

In an embodiment of the invention, the target gear determination device is provided to send information about the change in the target gear to the gearshift implementation device if a parameter indicating a high degree of probability is present. If the target gear changes, a shift is imminent. At the point in time when the setpoint gear is changed, it is just not yet clear whether a single or multiple shift is to be carried out.

The circuit execution device is intended to prepare the forthcoming circuit. For example, the switching elements, which will definitely be involved in the shift, can already be prepared for the shift. For example, the transmissible torque can already be slightly reduced when switching elements are switched off, or switching elements that are switched on can already be slightly activated. For example, when the shifting elements are actuated hydraulically, a filling phase of the clutch or brake to be engaged can be started.

As a result, as soon as the gear to be engaged changes, the shift can take place very spontaneously.

In an embodiment of the invention, the target gear determination device is provided to change the target gear in accordance with the probable change if a characteristic variable indicating a high probability of a further change in the target gear is present and to adopt the target gear thus changed immediately as the gear to be engaged. In this case, it is assumed that the driver of the vehicle wants a multiple shift, that is, for example, that he maintains the rate of change of the power demand signal until there is a further change in the setpoint gear. The driver of the vehicle thus receives very quick and spontaneous feedback on his change in the power requirement signal.

• 1 ein Prinzipbild eines Antriebsstrangs eines Kraftfahrzeugs mit einem automatischen Getriebe und einer zugehörigen Steuerungseinrichtung,
• 2 Schaltlinien zur Bestimmung eines Sollgangs des Getriebes,
• 3 einen zeitlichen Verlauf der Stellung eines Fahrpedals, eines Sollgangs und eines einzulegenden Gangs,
• 4 Ablaufdiagramm eines Verfahrens bei Änderung der Sollgangs,
• 5 eine zeitliche Darstellung von Betriebsgrößen des Kraftfahrzeugs bei einer Änderung des Sollgangs und
• 6 eine zeitliche Darstellung von Betriebsgrößen des Kraftfahrzeugs bei einer Änderung des Sollgangs bei einer alternativen Ausführungsform der Erfindung.

Further advantages of the invention emerge from the description and the drawing. Exemplary embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show in the drawing:

• 1 a schematic diagram of a drive train of a motor vehicle with an automatic transmission and an associated control device,
• 2 Shift lines for determining a target gear of the transmission,
• 3 a time course of the position of an accelerator pedal, a target gear and a gear to be engaged,
• 4 Flowchart of a procedure when changing the target gear,
• 5 a chronological representation of operating parameters of the motor vehicle when there is a change in the target gear and
• 6 a chronological representation of operating variables of the motor vehicle when the target gear changes in an alternative embodiment of the invention.

According to 1 a drive train 10 of a motor vehicle has a drive machine 11 in the form of an internal combustion engine, which is controlled by a control device 12 . The control device 12 has a signal connection to a power actuator 13 in the form of an accelerator pedal, by means of which a vehicle driver can specify a target value for the torque to be delivered by the drive engine 11 . The driver of the vehicle thus generates a power request signal which reflects a position of the accelerator pedal.

The drive machine 11 is connected to an automatic transmission 14 in the form of a planetary wheel change-speed transmission with 7 forward gears, which is controlled by a control device 15 . The control device 15 is in signal connection with a selector lever 16, by means of which the driver of the vehicle can select different driving stages of the transmission 14. The control device 15 has a. Desired gear determination device 21 and a shift implementation device 22. Desired gear determination device 21 determines a gear to be engaged, which gear shift implementation device 22 engages by correspondingly actuating shifting elements of transmission 14 (not shown). The determination of the gear to be engaged is based on the 2 , 3 and 4 explained in detail.

The transmission 14 is connected by means of a drive shaft 17 to an axle transmission 18 which, in a known manner, transmits the output torque of the drive engine 11 to driven vehicle wheels 20 via side shafts 19 .

The control devices 12 and 15 have a signal connection to one another via a serial bus connection, for example via a CAN bus. In this way, variables detected by the control devices 12 and 15 can be exchanged.

In 2 shift lines are shown which are stored in the target gear determination device 21 . For reasons of clarity, only a selection of downshift lines, ie lines that define the conditions for a reduction in the setpoint gear, are shown. The lines represent speeds (nab) at the output of the transmission, plotted against the position (pw) of the accelerator pedal. The speeds mentioned are proportional to the speed of the motor vehicle. The target gear changes when an operating point, which reflects the current speed nab at the output of the transmission and the current position pw of the accelerator pedal, crosses a shifting line. This is exemplified in the 2 shown. At time t1, the motor vehicle is at the operating point AP1 with a speed nab1 and a position pw1 of the accelerator pedal. The 4th gear is engaged in the transmission, so that a setpoint gear and the gear to be engaged each have the value 4. At time t2, the vehicle driver suddenly increases the position pw of the accelerator pedal very quickly. The corresponding courses of the position of the accelerator pedal, the target gear and the gear to be engaged over time are in 3 shown. Since the speed of the motor vehicle and thus the speed nab cannot change that quickly, nab remains constant. The operating point thus changes to the operating point AP2 with the same speed nab1 and a larger position pw2 of the accelerator pedal. With this change, the current operating point at time t3 exceeds the shift line 4-3 (SL_4_3), ie the downshift line from 4th to 3rd gear. The setpoint gear thus changes from 4th to 3rd gear at time t3. When the shift line is exceeded, the position of the accelerator pedal has the value pw_4_3.

On the basis of this change in the target gear, the target gear determining device determines a parameter k, which indicates a measure of the probability of a further change in the target gear. For this purpose, the setpoint gear determination device calculates the time gradient pw_p of the course of the position pw of the accelerator pedal at time t3. With a stored period of time dt_v, the target gear determination device estimates what value pw_v the position of the accelerator pedal will probably have at the point in time (t3+dt_v) if the gradient remains the same. The time period dt_v can be between 50 and 500 ms, for example. The following formula is used for this: $$\text{pw\_v}=\text{pw\_4\_3}+\text{pw\_p}*\text{dt\_v}$$

This would turn into 2 result in an operating point AP_v1. The setpoint gear determination device checks whether another shifting line would be exceeded when the operating point changes to the operating point AP_v1. This is the case in this example because the shifting line 3-2 (SL_3_2) would be exceeded. If the driver of the vehicle continues to press the accelerator pedal as assumed, the setpoint gear would change again. The parameter k the value 1, which indicates a high probability of another downshift. If no further shift line were crossed, the parameter k would have the value 0, which indicates a low probability of another downshift.

As a result of the fact that the parameter k has the value 1, the gear to be engaged remains at the value 4 even after the setpoint gear has changed at the time t3. Thus, no shifting is triggered at the time t3. At time t3, however, the target gear determination device sends information about an imminent downshift to the gearshift implementation device, which, in response to this, prepares the downshift.

Since the vehicle driver also increases the position pw of the accelerator pedal after time t3, the current operating point at time t4 exceeds shift line 3-2 (SL_3_2). The target gear thus changes at time t4 from 3rd to 2nd gear. In response to this, the setpoint gear determination device calculates a probable operating point AP_v2 in the manner described. Since no further switching line would be exceeded when setting this operating point, the parameter assumes the value 0. As a result, the gear to be engaged changes at time t4, as does the setpoint gear, to the value 2. The shift execution device thus starts a downshift from 4th to 2nd gear at time t4 and executes this shift as a multiple shift. The switching can take place very spontaneously, since it has already been prepared since time t3.

The vehicle driver continues to increase the position pw of the accelerator pedal even after time t4, until the operating point AP2 is reached. In this case, however, no further switching line is exceeded. The target gear therefore remains unchanged.

Analogous to the precalculation of the course of the position of the accelerator pedal, the course of the speed (nab) at the output of the transmission can also be determined on the basis of the rate of change of the speed (nab) at the time of the change in the target gear. The probable operating point can then be precalculated alone or additionally using the precalculated speed.

In 4 shows the sequence within the target gear determination device when the target gear changes. The sequence starts in step 30. In the following step 31, the target gear changes, so the operating point exceeds a shift line. In step 32, the future course of the working point is estimated, as described, and the parameter k is determined.

In query block 33 it is checked whether a further change in the target gear is likely. If the parameter k has the value 0, then in block 34 the gear to be engaged is set equal to the target gear and the sequence is ended in step 35. If the parameter k has the value 1, then in step 36 the device that implements the shift is informed about the forthcoming shift.

In query block 37 it is checked whether a stored period of time has elapsed since the setpoint gear in block 31 was changed. If so, then block 34 is executed as above.

If the period of time has not yet expired, it is checked in block 38 whether a termination condition is met. A check is made as to whether the gradient of the change in the position of the accelerator pedal has changed by more than a stored value since the precalculation in block 32 . If so, the process continues in block 34 as well.

If the termination condition is not met, it is checked in block 39 whether there is a further change in the target gear. If there is another change, the sequence starts again at block 31. If there is no further change, the sequence jumps back to block 37, so that queries 37, 38 and 39 are repeated until either the time period has expired or the termination condition is met is.

Instead of checking in block 37 whether a period of time has elapsed since the last change in the target gear, it can also be checked whether a period of time has elapsed since the start of the process, ie since the first change in the target gear.

In 5 shows the time curves of the speed of the prime mover, the target gear and the gear to be engaged in an application of the process described over time. A progression of the rotational speed for a procedure according to the prior art is also shown as a comparison.

The desired gear 40 and the gear to be engaged 41 each have the value 4 at time t1 3 and the above statements, the setpoint gear changes from value 4 to value 3 at time t3. The gear to be engaged remains unchanged. At point in time t4, setpoint gear 40 and gear 41 to be engaged change to 2nd gear. The course of the gear 41 to be engaged is reflected in the course of the rotational speed 42 of the prime mover. The speed increases only slightly until shortly after the gear 41 to be engaged has been changed. However, the speed 42 then increases very quickly and with an almost constant gradient to the target speed in 2nd gear. The short delay is due to the response times of the switching elements.

Without the use of the method according to the invention, the speed would change according to line 43 . In this case, a shift would be triggered at time t3, that is to say when setpoint gear 40 changes, and then another shift at time t4. However, these circuits could only be implemented as individual circuits, which would result in an inharmonious course of the speed. The speed would increase briefly, then remain almost constant and then increase again. This course would be uncomfortable and the target speed in 2nd gear would also be reached later.

In 5 are the same sizes as in 4 shown. The course of the target gear is identical to the course in 4 . The difference is that in 5 the gear 140 to be engaged jumps to 2nd gear at time t3 and a shift from 4th to 2nd gear is immediately triggered as a multiple shift. The speed 142 of the prime mover thus reaches the target speed in 2nd gear even more quickly.

Claims (11)

Control device for an automatic transmission of a motor vehicle - a target gear determination device (21) and - a circuit conducting device (22), wherein - the target gear determination device (21) determines a gear to be engaged, - the gear-shifting device (22) engages the gear to be engaged and - a shift sequence depends on whether the gear to be engaged deviates from an actual gear by one gear or by more than one gear, with the target gear determining device (21) being provided for this purpose, - to determine a target gear, - to determine a parameter (k) when there is a change in the target gear, which indicates a measure of the probability of a further change in the target gear and - to determine the gear to be engaged as a function of the target gear and the named parameter (k) and the target gear determining device (21) is also provided for this purpose, - If there is a characteristic variable (k) indicating a low probability of a further change in the target gear when the target gear changes, to immediately accept the changed target gear as the gear to be engaged and - If there is a parameter indicating a high probability of a further change in the target gear when there is a change in the target gear, not to immediately adopt the changed target gear as the gear to be engaged. control device claim 1 , characterized in that the target gear determination device (21) is provided to - determine the target gear as a function of a power requirement signal and/or a speed signal and - determine the parameter (k) as a function of a rate of change of the power requirement signal and/or the speed signal. control device claim 2 , characterized in that the power request signal is designed as a position of an accelerator pedal (13). control device claim 2 or 3 , characterized in that the target gear determination device (21) is provided for determining the parameter (k) to estimate a course of the power requirement signal using the rate of change (pw_p) of the power requirement signal. control device claim 2 , 3 or 4 , characterized in that the setpoint gear determination device (21) is provided for the purpose of estimating a course of the speed signal with the aid of the rate of change of the speed signal in order to determine the parameter (k). control device claim 4 or 5 , characterized in that shifting lines (SL_4_3, SL_3_2, SL_2_1) are stored in the target gear determination device (21), the target gear changing when an operating point of the motor vehicle that is dependent on the power requirement signal and/or speed signal exceeds a shifting line and the target gear determining device (21) to do so provision is made to determine the parameter (k), - which indicates a high probability of a further change in the target gear if the predicted working point exceeds a further shifting line and - which indicates a low probability of a further change in the target gear if the predicted working point does not exceed any further switching line. control device claim 1 , characterized in that the desired gear determines Measuring device (21) is provided to adopt the target gear as the gear to be engaged after a settable and storable period of time has elapsed if a parameter (k) indicating a high probability of a further change in the target gear is present. control device claim 7 , characterized in that the target gear determination device (21) is provided to check a termination condition if a parameter (k) indicating a high probability of a further change in the target gear is present, and the changed target gear upon fulfillment of the termination condition or at the latest after expiry of the adjustable period of time as the gear to be engaged. control device claim 1 , 7 or 8th , characterized in that - the target gear determination device (21) is provided to send information about the change in the target gear to the gearshift implementation device (22) if a parameter (k) indicating a high probability of a further change in the target gear is present and - The circuit implementation device (22) is intended to prepare the forthcoming circuit. control device claim 1 , characterized in that the target gear determination device (21) is provided to change the target gear according to the probable change in the event of the presence of a parameter (k) indicating a high probability of a further change in the target gear and to change the target gear thus changed immediately as a gear to be engaged to take over. Method for operating an automatic transmission (14) of a motor vehicle with a control device (15) which has a target gear determination device (21) and a gearshift implementation device (22), wherein - the target gear determination device (21) determines a gear to be engaged, - the gear-shifting device (22) engages the gear to be engaged and - a shift sequence depends on whether the gear to be engaged deviates from an actual gear by one or more than one gear, with the target gear determining device (21) - determines a target gear, - If there is a change in the target gear, a parameter (k) is determined which indicates a measure of the probability of a further change in the target gear and - determines the gear to be engaged as a function of the target gear and the named parameter (k) and the target gear determining device (21) is also provided for this purpose, - If there is a characteristic variable (k) indicating a low probability of a further change in the target gear when the target gear changes, to immediately accept the changed target gear as the gear to be engaged and - If there is a parameter indicating a high probability of a further change in the target gear when there is a change in the target gear, not to immediately adopt the changed target gear as the gear to be engaged.

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