Patent Application
20060293825
The invention concerns a method for operating a motor vehicle with a speed and/or distance control device, the same as with an automatic transmission, in which starting from an actual driving speed, a preset nominal driving speed is autonomously controlled, in which the adaptation of the actual driving speed to the nominal driving speed is controlled by a ratio change of the automatic transmission and in which the ratio change control is carried out based on a virtual accelerator pedal value derived from the real deviation of the accelerator pedal by the driver. The invention further concerns according to claim 16 a device for applying such a method and according to claim 26 a vehicle equipped so that on this method and device can be purposefully operated.
It is known that a motor vehicle can be equipped with a so-called speed control unit which enables the driver to constantly keep a driving speed established by him without the wheel torque having to be manually controlled at the same time. With such a speed control unit, it is also possible to automatically reach and control a previously stored speed again.
Inasmuch as in a motor vehicle thus equipped an automatic transmission is also built up; it is possible by adequate automatic selection of the transmission ratio to assist the functions of the speed control unit so as to make available to the driver greater power reserves and better driving characteristics, depending on the environmental conditions of the vehicle, especially on the gradient of the road.
With this background, it is known from DE 38 75 206 T4 that an optimal cooperation of the control functions for adjustment of the reduction ratio of an automatic transmission and of the speed control function of speed control device can consist, for example, in maintaining a driving speed preset by the driver speed controller first compares the adjusted speed with the actual driving speed and, according to the speed difference found, actuates a power adjusting element, such as a throttle valve on an internal combustion engine of the vehicle, which serves as a prime mover.
Inasmuch as the road often has gradient changes on account of the comparatively slow reacting prime mover to the quick performance change settings, fluctuations result in the driving speed which can be reduced, for example, by changing the transmission reduction ratio. To that end, DE 38 75 206 T4 proposes a driving control system for a motor vehicle having a continuously adjustable force transmission in which a throttle valve of a motor can be adjusted, via an adjusting element, so that the driving speed and the adjusted speed converge and which has ways for lowering the reduction ratio. In this drive control system, it further contains a switch to be manually actuated for producing an acceleration signal which causes the adjusting element to open the throttle valve, such that said ways correspond to the acceleration signal produced and that the reduction ratio is reduced by a predetermined amount.
It is disadvantageous in this speed control and ratio changing system that in it is used a manually produced acceleration signal directly for ratio control and besides the taking into account of other driving state parameters is not implemented.
From DE 101 15 052 A1 are also known a method and device for adjusting a transmission ratio in a motor vehicle with distance and/or driving speed control. From said publication is to be deduced that in a conventional motor vehicle having an otto-motor, the throttle valve is mechanically controlled directly by accelerator pedal deviation. Hereby result in a non-linear accelerator pedal torque characteristic familiar to skilled drivers.
In vehicles having mechanical decoupling of accelerator pedal and performance adjusting element of the internal combustion engine, however, the driver no longer mechanically assumes the throttle valve position by an accelerator pedal deviation, but signalizes thereby his desired performance or the motor output torque desired. To be able to convert this desired performance to a signal for adjusting the performance adjustment element of the internal combustion engine, the actual accelerator pedal position is coordinated with a motor performance with the aid of a characteristic field to the valve of which the performance adjusting element is adjusted.
The transmission ratio of an automatic transmission is also known and is usually adjusted depending essentially on the motor load (throttle valve position) and on the driving speed.
To maintain the non-linear accelerator pedal motor torque characteristic to which the driver is used, in a combination of motor control system in which the accelerator pedal and the performance adjusting element of the internal combustion engine are mechanically uncoupled with conventional transmission control, the transmission gearshifts are carried out based on a so-called “virtual accelerator pedal valve”. This virtual accelerator pedal valve now no longer corresponds here to the driver's torque or performance desire, but to the real accelerator pedal valve (that is, accelerator pedal angle) at which the required vehicle propulsion adjusted.
By this procedure, in a reciprocal action with the control function of the driving speed controller, a problem appears when the nominal torque preset by the latter of the internal combustion engine is close to the maximum torque of this prime mover. In this area, a small change of the nominal torque leads already to a great step in the virtual accelerator pedal valve whereupon a change of the reduction ratio is spontaneously triggered by the transmission control. Especially in case of only a small difference between said nominal torque and the maximum motor torque, this transmission shift disturbs the vehicle driver.
According to the method introduced in DE 101 15 052 A1, those disturbing shifts during the speed control operation are prevented or delayed. It is provided for the purpose that in the normal operation of the vehicle, that is, without speed control function, the performance adjusting element of the internal combustion engine is controlled according to the accelerator pedal position and to a non-linear characteristic field of the bevel engine torque. The ratio of the automatic transmission is here controlled in a conventional manner.
During the speed control operation there is produced by the adjustment of the speed control unit a preset nominal value by means of a characteristic field inverse to the first mentioned characteristic filed (that is, a motor torque-bevel characteristic field) and inverse or virtual accelerator pedal value which, in accordance with the actual torque of the prime mover, is used directly or after a value limitation to the ratio control of the automatic transmission. This method and the appertaining device are criticized as imperfect.
Against this background, the invention is based on the problem of introducing a method and device for operating a vehicle speed controller and for adjusting the ratio of an automatic transmission in a motor vehicle with which a pendular shift is prevented better than formerly and spontaneous acceleration operations are possible by changing the transmission reduction ratio. In addition, a vehicle is introduced which is equipped so that therewith the method and the device can be used.
The solution of the problem results for the device from the features of the main claim and for the method from the independent claim 16. According to claim 26 the invention concerns also a vehicle with which an inventive method can be applied to said device. Advantageous embodiments and developments of the invention can be understood from the dependent claims.
For a better understanding of the invention features mentioned herebelow, it is indicated, relative to the method, that by blocks, function blocks, processing blocks, calculation blocks, modules, comparators, etc., program steps, program modules or sub-programs is meant by at least one superposed control and regulation program. The at least one control and regulation program is worked off in a separate computer, a transmission control unit, a speed control unit and/or in a distance control unit. To that extent, said blocks, function blocks, processing blocks, calculation blocks, modules, comparators or others can also be implemented as device component parts, such as fixed coordinated computer structures.
The invention accordingly relates to a method for operating a motor vehicle with a speed and/or distance control device, the same as with an automatic transmission in which, departing from an actual driving speed, a preset nominal driving speed is autonomously controlled, in which the adaptation of the actual driving speed to the nominal driving speed is controlled by a ratio change of the automatic transmission and in which the ratio change control is carried out based on a virtual accelerator pedal valve derived from the actual deviation of the accelerator pedal by the driver, the specification of the virtual accelerator pedal value being controlled by the deviation of the actual vehicle speed relative to the nominal driving speed, by the vehicle longitudinal acceleration or vehicle longitudinal retardation and/or by the torque of the prime mover of the vehicle.
In this method, the virtual accelerator pedal valve is preferably changed in small incremental steps. This is of special advantage particularly during a ratio change operation in a continuously variable reduction-ratio changing automatic transmission, such as a CVT.
According to another advantageous design of the inventive method, it is provided that for ensuring as dynamic as possible a start of the ratio change, the virtual accelerator pedal value is changed for introducing a ratio change by an offset value of a magnitude greater than that of an incremental change of the same.
Moreover, it is deemed advantageous for controlling the start of the ratio change if for determining the virtual accelerator pedal value reaching and/or falling below at least one preset motor torque threshold value is taken into account.
In this connection, for determining the virtual accelerator pedal value, it can also be logical if reaching or exceeding at least one preset threshold value of a relative motor torque is taken into account, the relative motor torque being defined as the ratio of the actual motor torque to the maximum possible motor torque at the determined rotation speed of the motor.
In addition, it is deemed convenient for determining the virtual accelerator pedal value if, therefore is taken into account, the reaching and/or exceeding of at least one preset threshold value for the driving speed and/or the reaching an/or exceeding of at least one preset threshold value of the longitudinal acceleration of the vehicle.
Insofar as during a constant speed control operation, when the tractional resistance of the vehicle increases, a preset nominal driving speed is again to be reached then, according to a preferred embodiment of the inventive method, the motor torque is first increased and then, when the motor torque emitted by the prime mover is not enough to keep or reach the nominal driving speed again, starting from a predetermined driving speed deviation to nominal driving speed, the virtual accelerator pedal value is gradually increases. This gradual increase of the virtual accelerator pedal value to the ratio change control is terminated when the motor power suffices to reach at least a predetermined longitudinal acceleration of the vehicle.
Furthermore, in a driving sped resumption control for again reaching a preset nominal driving speed, starting from an actually lower driving speed to the decision of whether the virtual accelerator pedal value should be increased, it can be of advantage to evaluate between the actual driving speed and the nominal driving speed, together with the speed difference, the exceeding of motor torque threshold or of a threshold value of the relative motor torque. It is, in addition, advantageous to also check that the vehicle longitudinal acceleration threshold value F has not been exceeded.
It also can be provided that when the motor torque suffices to raise the vehicle speed to the nominal driving speed with a vehicle longitudinal acceleration above the threshold value F, a change of ratio of the transmission is eliminated.
It can finally be provided that the virtual accelerator pedal value for carrying out a transmission upshift be gradually reduced when the motor torque falls below a preset torque threshold value and the virtual accelerator pedal value is higher than a predetermined minimum value for the virtual accelerator pedal value.
A concrete method for carrying out a constant speed driving mode based on a preset nominal driving speed can be operated regarding the speed and/or distance control device, the same as an automatic transmission, as follows. Determining a reduction of the driving speed from the preset nominal driving speed by a preset driving speed differential amount. Increase the motor torque by control of the performance adjusting element of the vehicle prime mover. Insofar as during a preset motor rotational speed, the prime mover emits its maximum torque, the driving speed drops below a preset threshold value N and the vehicle longitudinal acceleration has, compared to the initial situation, an insufficient acceleration value, release a timer. After expiration of a preset time interval t3-t4, when the prime mover still emits its maximum torque at the current rotational speed and the driving speed is below the driving speed threshold value N, the same as the vehicle longitudinal acceleration is below a longitudinal acceleration threshold value F, add the offset value to the actual virtual accelerator pedal value and thereby begin a transmission downshift. Incremental increase of the virtual accelerator pedal value and therewith going on transmission downshift until the vehicle longitudinal acceleration has reached a preset positive acceleration threshold value G. Terminate the incremental increase of the virtual accelerator pedal value and thus end the downshift. Reduce the motor torque when the driving speed has reached the nominal driving speed.
Another method or resuming a preset nominal driving speed can be operated with regard to speed and/or distance control device and to the automatic transmission as follows. At a driving speed below a preset threshold N, raise the motor torque to a torque threshold value. When upon reaching said torque threshold value the driving speed is still below the speed threshold value N and the vehicle longitudinal acceleration has a value below the threshold value F, release a timer. After expiration of a preset time interval t9-t10, when the the prime mover emits its maximum torque at the current rotational speed and the driving speed is below the speed threshold value n, the same as the vehicle longitudinal acceleration has a value below the threshold value F, add an offset value to the virtual accelerator pedal value and therewith being a transmission downshift. Incremental enlargement of the virtual accelerator pedal value and therewith going on added transmission downshift until the vehicle longitudinal acceleration has reached a preset positive threshold value G. Terminate the incremental increase of the virtual accelerator pedal value and therewith end the downshift. Reduce the motor torque when the driving speed has reached the nominal driving speed.
One other method for resuming a preset nominal driving speed can be operated with regard to speed and/or distance control device, the same as to the automatic transmission, as follows. At a driving speed below a preset speed threshold value N, increase the motor torque up to a torque threshold value. Upon reaching said torque threshold value, when the driving speed is still below the speed threshold value N and the vehicle longitudinal acceleration has a value below the threshold value F, release the timer. After expiration of a preset time interval t9-t10, when the prime mover emits its maximum torque at the current rotational speed and the driving speed is below the speed threshold value N, the same as the vehicle longitudinal acceleration has a value below the threshold value F, add an offset value to the virtual accelerator pedal value and begin a transmission downshift. Incremental increase of the virtual accelerator pedal value and therewith going on downshift until the accelerator pedal value has reached a predetermined maximum accelerator pedal value. Terminate the downshift when the vehicle longitudinal acceleration has not exceeded a value G but the driving speed has reached a driving speed value O close to the nominal driving speed or has reached the nominal driving speed proper. Reduce the motor torque.
A method for resuming a preset nominal driving speed or for covering a route at constant driving speed can be operated with regard to a speed and/or distance control device, the same as to the automatic transmission, as follows. Inasmuch as the prime mover emits its maximum torque at the precise existing motor rotation speed, the driving speed is above an upper speed threshold value O and the virtual accelerator pedal value is between a maximum and a minimum value, reduce the motor torque. Insofar as the motor torque has reached a lower threshold value and the above mentioned conditions still hold, start a timer. When a predetermined time period has expired and the above mentioned conditions still hold, being a transmission upshift by incremental reduction of the virtual accelerator pedal value. Regulate the motor torque starting from a moment t17 to constant maintenance of the vehicle speed. Terminate the upshift operation by ending the reduction of the virtual accelerator pedal value when this has reached a predetermined minimum value or terminate the upshift operation by ending the reduction of the virtual accelerator pedal value when the motor torque has reached a predetermined upper threshold value of the torque which is between the lower torque threshold value and the maximum motor torque that can be emitted at the current rotational speed.
As has been stated, the invention also relates to a device in a motor vehicle for applying at least one of the above methods with one speed and/or distance control device, one prime mover, one motor control unit, one automatic transmission, one transmission control unit and one computer where the computer is associated, according to signal technique, with the motor control unit, the transmission control unit and the speed/distance control device or is identical with one of said units. The device is further characterized by the computer having the following component parts: one input module for receiving information relative to the actual control status of the speed and/or distance control device; one initialization module for determining a virtual accelerator pedal value from the actual accelerator pedal actuation; one determination module to determine the motor torque, the vehicle acceleration and the difference between the actual driving speed and a preset nominal driving speed; one determination module to determine the actual status of the assistance of the speed control function by changing the transmission reduction ratio; one calculation module to calculate the actual virtual accelerator pedal value and one output module to issue the actual accelerator pedal value to the transmission control unit for control of the reduction ratio.
Regarding the initialization module it is preferably provided that it has one inquiry module where is determined whether the speed control device and/or the distance control device is active for the first time since the last starting operation of the vehicle or the last driving speed control assistant; the allocation module which in case of negative result of the inquiry in the inquiry module allocates the actual virtual accelerator pedal value for subsequent processing, and one processing block to be used in case of positive result of the inquiry and in which are determined the actual starting values for the virtual accelerator pedal value and the status value of assistance of the speed control or distance control device with regard to the transmission ratio operations.
Preferably the processing block has one calculation block in which the actual real accelerator pedal value can be checked in a maximum value generator as to whether said real accelerator pedal value is higher than a minimum value for the virtual accelerator pedal value; there being issued as output parameter of this maximum value generator, the existing value higher than the actual virtual accelerator pedal value.
It is also provided in this connection that the processing block comprises one other calculation block the input parameter of which is the precisely determined virtual accelerator pedal value that, in this other calculation block, it can be inquired in comparison step whether the actual virtual accelerator pedal value is higher than the minimum value for the virtual accelerator pedal value and that the output of said comparison step is connected with the other processing block with regard to a positive reply and with an additional processing block with regard to a negative reply, it being possible with the other processing block to set at two the status value in a status value memory and with the additional processing block to set at zero the status value in the status value memory.
The calculation module for calculating the actual virtual accelerator pedal value preferably has one first increment generator for an increase of the virtual accelerator pedal value, one second increment generator for a reduction of the virtual accelerator pedal value and one zero value increment generator.
It is further provided that the calculation module for calculating the actual virtual accelerator pedal value has one status memory for storing status code numbers (zero, one, two, three) which, in this sequence, indicate whether no activity is to take place regarding a change of the virtual accelerator pedal value, whether an increase of the virtual accelerator pedal value takes place at the time, whether at the time an existing virtual accelerator pedal value is to be kept or whether at the time an existing virtual accelerator pedal value is to be reduced.
This calculation module, in addition, has one program switch which is connected via additional elements with said increment generators. To update the existing virtual accelerator pedal value, it is further provided that via a feedback the virtual accelerator pedal value of the last calculation loop can be supplied to the addition elements.
In another development of the device for applying the introduced method, it is provided that with the program switch it is possible to relay the incrementally changed virtual accelerator pedal value for further processing, which was changed according to the assistance status just valid and stored in the status memory.
In addition, the calculation module for calculating the actual virtual accelerator pedal value has a minimum value memory for a determinable lower limiting value and a maximum value memory for a determinable upper limiting value of the virtual accelerator pedal value, the outlet of the program switch being connected with the inlet of a first comparator also connected with the minimum value memory. Besides, the outlet of the first comparator is connected with the inlet of a second comparator which is also connected with the maximum value memory. Therefore, at the outlet of the second comparator outcrops the virtual accelerator pedal value which corresponds to the established minimum value or to the established maximum value or is between the two values.
Finally, the invention also concerns a motor vehicle. The transmission is designed as an automatic transmission continuously changing the reduction ratio, for example, as CVT with beveled pulley.
To make clear the invention, enclosed with the description is a drawing with the aid of which one embodiment of the invention with other features and advantages is explained in detail herebelow. The drawing shows:
While with the internal combustion engine 130 a motor control unit 137 is coordinated, the automatic transmission 131 is controlled by a control device 136. Both control units are connected via one line 139 for interchanging information.
Furthermore, with this vehicle drive train is coordinated one speed control device and/or one distance control device 141 symbolized by the two arrows and which receives for its control activities necessary information from sensors and/or adjusting devices, the same as, if needed, from other control units. To the extent, that a distance control device is used, the driving speed control function thereof is of special interest in relation to the instant invention. As one of its output parameters this device 141 communicates to one computer 2, here separately designed, information concerning its actual driving speed state. This parameter is taken up by the computer 2 in an inlet area 1 and further processed as described below.
As other input parameters, the computer 2 takes up values like the motor torque B, the vehicle speed C, the vehicle acceleration D and the accelerator pedal deviation angle designated herebelow as real accelerator pedal value 15.
In addition, the computer 2, via a control line 140, can act upon the motor control device 137 which for its part acts for adjusting the motor torque to the performance adjusting element 138 of the internal combustion engine 130.
Finally, the computer 2 has internal calculation modules with which, from the information taken up, in the manner to be described above, the virtual accelerator pedal value J is formed and relayed via an outlet area 3 to the transmission control unit 136 for change of ratio of the automatic transmission 131. The virtual accelerator pedal value, briefly said, is determined according to the motor torque B, the vehicle speed C, the vehicle acceleration D, the accelerator pedal value 15 and the actual speed control functions of the speed control and/or distance control device 141.
It is not indispensable that the computer 2 be designed as separate unit. It can be also component part of the transmission control unit 136, of the motor control unit 137, or of the speed an/or distance control device 141 without for this reason the structure and mode of operation of said coordinated functions having to be substantially different.
The inner construction and mode of operation of the computer 2, the same as the interaction thereof with other control units or aggregates of the vehicle, will be described above.
To the extent that individual components of the drawing are designated as blocks, function blocks, processing blocks, calculation blocks, modules, comparators or other, with them are meant program steps, program modules or subprograms of a superposed control and regulation program. This at least one control and regulation program can be operated in a computer 2, in a transmission control unit 136, a speed and/or distance control unit 141 or in a motor control unit 137. To that extent, said blocks, function blocks, processing blocks, calculation blocks, modules, comparators and others, can also be implemented as device component parts such as fixedly coordinated computer structures.
Function block 1 symbolizes the inlet area of the computer 2 or a signal in relation to the start up of the speed control function of the speed control or distance control device 141, which in the Figures of this embodiment of the invention, is also designated as “Tempomat.” The starting status thereof is accordingly relayed as an input parameter to the computer 2 which controlled thereby calculates a virtual accelerator pedal value which can be used for determining and adjusting the transmission reduction ratio optimal of the driving situation.
In a processing block 6, the motor torque, relative motor torque, vehicle longitudinal acceleration and the driving speed difference between a preset nominal driving speed and the actual driving speed are detected or calculated.
An acceleration pedal value J calculated is shown as an initial parameter in
Prior to calculation of the virtual accelerator pedal value in a calculation block 7, an initialization (block 4) of the calculation process is first undertaken in the computer 2. In block 5 is then determined the actual status of the driving speed control assistance for adaptation of the transmission reduction ratio in a manner suitable to the driving situation. For the purpose, the vehicle longitudinal acceleration or vehicle longitudinal retardation information (block 5) is used relative to the actual motor torque, the same as, if needed, to an eventual difference of the driving speed from a nominal driving speed preset to the driving speed control manually or automatically, for example, by a vehicle distance control.
The status of the driving speed assistance is here expressed by a parameter “A” which can assume an integral value from zero to three (block 5). The value zero stands here for “no shifting activity”, the value one for “at the moment ongoing downshift” (increase virtual accelerator pedal value), the value two for “keep active the transmission ratio at the moment” (keep virtual accelerator pedal value) and the value three for “upshift ongoing at the moment” (reduce virtual accelerator pedal value); see also block 112.
The program structure for initializing the calculation process, according to block 4, is shown in detail in
As long as the driving speed control is active for the first time in this operation phase, it is branched to a calculation block 12 in which the starting value for the status A of assistance of the driving speed control by the transmission and for the virtual accelerator pedal value are determined. For the purpose, in a calculation block 13, the actual measured real accelerator pedal value 15 (for example, accelerator pedal deviation angle) is comparted with an established minimum value 16 for the virtual accelerator pedal value in a maximum value generator 17. If the real accelerator pedal value 15 is higher than the minimum value, the latter is issued from the maximum value generator 17.
A temporary virtual accelerator pedal value 18 thus obtained is then checked in a calculation block 14 in a comparison step 19 in the sense of whether the virtual accelerator pedal value 18 just determined is higher than the minimum value 16 for the virtual accelerator pedal value. If this is so, then it is decided that the status value A for the driving speed control assistance be set at the value two and the actual virtual accelerator pedal value be maintained (processing block 20).
Insofar as the virtual accelerator pedal value 18 is not higher than the minimum value 16, no further activity is carried out and the status value A for the driving speed control assistance is set at zero (processing block 21).
In a calculation block 25,
It is accordingly checked in a processing block 30 with an inquiry 31 whether the driving speed control is in an acceleration mode and in an inquiry 32 determined whether the speed difference between the actual driving speed and the preset nominal driving speed is higher than a preset threshold value. If at least one of the two inquiries in a condition module 33 turns out positive, in another inquiry module 37, it is determined whether the vehicle longitudinal acceleration is below an acceleration threshold value (threshold 2) (comparison module 34), whether the relative motor torque is greater than a relative motor torque threshold value (threshold 1) (block 35) and whether at the time just no transmission downshift occurs (A unlike one). If all said conditions for introducing a downshift are met, a timer is started (command 38). If this is not so, then the timer is set at the value zero (command 39).
In the processing block 40 it is checked in an inquiry block 41 whether the timer has been set so high that a preset maximum time (“threshold”) has been exceeded or the preset time interval has expired. If this is so (comparator 43) and, at the moment, no activity of the driving speed assistance is to be registered according to a processing step 42 (A=zero), the virtual accelerator pedal value is raised by one offset value (process step 44) and thus a downshift of the transmission is started. The offset value is here preferably greater than an incremental change value for determining the actual virtual accelerator pedal value. This produces a better dynamic, especially at the start of the downshift.
In a processing block 50 is shown that, according to the process step 51, after expiration of the timer with regard to the same time interval from block 40, according to process step 52, the status of the driving speed control assistance is set at the value A=one and the timer is set at the zero value.
If the reply to method steps 63 and 64 in a comparator 65 is positive or it has been established in an inquiry 66 that the inquiry 62 was replied in the affirmative, it is additionally examined in an inquiry 67 whether the question 61, with regard to the downshift, had a positive reply also. When said conditions have been met, the downshift of the transmission is terminated and, according to process step 68, the status of the driving speed control assistance is set at the value A=two whereby the virtual accelerator pedal value applicable a the time is maintained.
Accordingly, in a block 70 it is checked in process steps 71 to 73 whether the actual virtual accelerator pedal value is higher than or equal to the already mentioned minimum value for the virtual accelerator pedal value; whether the relative motor torque is smaller than a relative motor torque threshold (threshold 2) and whether the speed difference between the actual driving speed and the preset nominal driving speed is lower than a preset threshold value (threshold). If the examination of said three conditions in a working step 74 shows that they have been met for introducing an upshift, the timer is started according to a process step 75. If that is not the case then, according to a process step 76, the timer is set at the zero value.
As a processing block 80 shows, following the process step 75, it is checked in a process step 81 whether a preset time interval has lapsed in the timer. If this is so, according to a process step 82, the status of the driving speed control assistance is set at the value A=three, which identifies an upshift precisely going on, that is, a breakdown of the virtual accelerator pedal value and the timer is set at the zero value.
To terminate a precise ongoing upshift, it is inquired in the processing block 90 in process steps 91 to 93 whether the relative motor torque is above a relative motor torque threshold (threshold 1); whether the virtual accelerator pedal value is higher than a preset minimum accelerator pedal value and whether the status of the driving speed control assistance is at the value A=three, that is, an upshift has just been carried out. Insofar as according to a comparison inquiry 95 said three conditions apply, according to a process step 95, the status of the driving speed control assistance is set at the value A=two. This means that if during an upshift operation the motor torque becomes too great, the upshift is terminated and in the state that follows the virtual accelerator pedal value is first kept constant.
Alternative to this, according to a processing block 100, an upshift terminates when the virtual accelerator pedal value is reduced to a value lower than or equal to the preset minimum of the virtual accelerator pedal value. It is, therefore, examined in a step 101 whether the virtual accelerator pedal value is lower than or equal to said minimum of the virtual accelerator pedal value and whether the status of the driving speed control assistance is set at the value A=three (ongoing upshift) (comparison inquiry 102). If both questions are answered in the affirmative, the status of the driving speed control assistance is set at A=zero in a process step 104 which means that no other activity occurs relative to the transmission.
In a further processing block 112,
The program switch 122 can assume three shifting positions in which it connects its input side alternatively to each other with one of three adding elements 119, 120 and 121. To said adding elements 119, 120 and 121 is fed, so to say, regenerated from the last calculation loop, the actual virtual accelerator pedal value J and from increment memories are loaded with increments 116 for an increase or increments 117 for a reduction of said actual virtual accelerator pedal value or are left unchanged (an increment memory 118 with increment=zero).
Since the program switch 122, depending on the precise actual assistance situation with introduced driving speed control, can shift between the three shift positions one=“ongoing downshift”, three=“ongoing upshift” and zero or two=“no activity” or “maintain shift”; the virtual accelerator pedal value is adapted in small incremental steps based on the existing situation so that transmission shifting operations are carried out in an optimal driving dynamic way without pendular shifting inclination.
As
As these explanations make clear, according to the invention an actual virtual accelerator pedal value is calculated by gradual buildup, breakdown or maintenance of the former virtual accelerator pedal value from the last program cycle. But characteristics or comparison and calculation operations of the actual program course also depend on the previously determined state or status of the assistance of the driving speed control by transmission shifting operations.
Accordingly, in a schematized diagram,
The curve A identifies here the status value of the driving speed control assistance; a curve B, the course of the relative motor torque; a curve C, the driving speed; a curve D, the nominal driving speed preset to the speed control; a curve E, the vehicle longitudinal acceleration; a straight line F and threshold value “threshold 2”, and a straight line G, a threshold value “threshold 1” for the vehicle longitudinal acceleration; a straight line H, a minimum value for the virtual accelerator pedal value; a curve J, a cycle of the virtual accelerator pedal value 127; a straight line K, a maximum value for the virtual accelerator pedal value; a straight line L, a threshold value for the relative motor torque; a straight line M, the 100% mark of the relative motor torque, and a straight line E=O, the zero line of the vehicle longitudinal acceleration.
As can be seen from
By increasing the tractional resistance caused, for example, by an increased road gradient, the driving speed C becomes reduced from the moment t1 so that by the driving speed control 141 action is exerted directly or via the computer 2 and/or the motor control device 137 upon a performance adjusting element 138 of a vehicle prime mover 130 in the sense of raising the motor torque B. Thereby the positive and thus also the relative motor torque B increase until the motor torque B has reached the maximum value at this motor rotational speed and with regard to its other time curve coincides with the 100% mark M of the relative motor torque until again reaching the nominal driving speed.
Starting from the moment t3 the driving speed falls below a lower threshold value N in relation to the nominal driving speed D. By this occurrence is started a timer which allows a preset time interval t3-t4 to lapse. Within said time interval t3-t4, if the driving speed C does not rise again above the speed threshold N, at the moment t4, a transmission downshift is introduced which is identified particularly by the change of status of the speed control assistance A from a value zero to the value one.
As
At the end of the downshift operation at the moment t5, the vehicle motor still runs at full load (B=M) while the vehicle longitudinal acceleration E, after exceeding a first threshold value F, has also exceeded an upper threshold value G. The driving speed C increases agin at this moment.
It can also be seen in
The assistance of the speed control mechanism by a time-oriented transmission ratio change in the sense of a downshift leads in the other time curve starting from the moment t6 to a best possible adaptation of driving speed C and nominal driving speed D so that now the motor torque B controlled by influence of the accelerator pedal control is reduced again to below the 100% mark (threshold value M) of the relative motor torque.
According to the inventive method, for deciding whether the virtual accelerator pedal value J must be increased, there are evaluated, together with the speed difference between the positive driving speed C and the nominal driving speed D, also the reaching of a preset relative motor torque threshold L, the same as in addition the vehicle longitudinal acceleration E. It is thereby obtained that the nominal driving speed D, under adequate environmental conditions, be exclusively reached by the existing motor torque B and, if needed, a transmission downshift can be prevented.
From the diagram shown in
At the moment t8 said resumption mode is activated in the speed control by a corresponding control command triggered, for example, by the vehicle driver or by an autonomously working distance control system. In consequence hereof, the speed control acts according to signalizing technique upon the performance adjusting element of the prime mover so that the latter is led to emitting a higher motor torque B. At the moment t9, as soon as the motor torque B has reached the threshold value L, a timer is started. In
After expiration of a preset time interval t9-t10, when the motor torque B still is above the threshold value L, the value of the vehicle speed is below the threshold value N and the vehicle longitudinal acceleration is below the threshold value F, the status value A for the program switch 122 is set at one. Thereby the virtual accelerator pedal value J affecting the transmission shifting operation is first gradually raised by an offset value above the former minimum value H and during the ongoing downshift raised by addition of incremental low values to always higher values. In this phase, the prime mover of the vehicle emits its maximum torque B.
At the moment t11, as soon as the vehicle longitudinal acceleration E has reached a preset upper threshold value G, this is considered as a signal for terminating the downshift operation. Therefore, at the moment t11, the status value A for the program switch 122 is set at the value two. This results in that the program switch 122 does not further increase the precisely valid virtual accelerator pedal value J.
By virtue of the reduction ratio now adjusted, the vehicle longitudinal acceleration E rises further in the time interval t11-t12 in order then, before reaching the moment t12, to drop to the value zero. Just then, when the acceleration has reached the value zero, the motor torque B is again reduced to below the torque threshold value L by acting upon the performance adjusting element of the vehicle prime mover. The driving speed C then reached at the moment t12 the nominal driving speed D, as desired.
In a variant of the downshift operation just described, during a driving speed resumption function, the acceleration operation develops comparatively slower, as can be understood with reference to the curves shown in bold dots. Accordingly, a vehicle longitudinal acceleration C′ does not reach the upper acceleration threshold G after beginning of the transmission downshift at the moment t10. Therefore, the status value A for the program switch 122 is kept for a comparatively long time at a value one (curve A′) so that a virtual accelerator pedal value J′ is increased until there has been reached the maximum value K for the virtual accelerator pedal value J′ stored in the maximum value memory 135.
In this case, the end of the downshift operation is established by the driving speed C′ reaching at the moment t12 a predetermined threshold value O below the nominal driving speed D. If this has occurred, then the status value A for the program switch 122 is set at the value two. The nominal driving speed D is reached at the moment t13 from the actual driving speed C′ during this resumption function of the driving speed.
By the full load operation of the prime mover the driving speed C rises continuously in the interval t14-t15. Shortly after said driving speed C has reached its upper threshold value O, the motor torque B lowers due to the action upon the performance adjusting element of the vehicle prime mover. As soon as the latter has reached at the moment t16 a value below the threshold value Q, a timer is started.
Insofar as after expiration of predetermined time interval t16-t17, the motor torque B is still below the threshold value Q and the vehicle speed above the threshold value O, the status value A for the program switch 122 is set at the value three which means that a transmission upshift is carried out by lowering the virtual accelerator pedal value. At the same time the motor torque B is regulated from a moment t17 to constant keeping of the vehicle speed.
At the beginning of the upshift at the moment t17, the driving speed C has reached the nominal driving speed D while by changing said status value A, the virtual accelerator pedal value J is reduced by small steps. As soon as the virtual accelerator pedal value J has at the moment t20 reached the minimal value H established in the minimum memory 124 for the virtual accelerator pedal value J, the status value A for the program switch 122 is set at the value zero which means that there will be no further activity relative to the transmission whereby the upshift is terminated.
One variant of this is shown by the curves in bold dots. Accordingly, at the moment t18 the motor torque B″ is more sharply increased than in the embodiment shown in the first variant according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 025 741.8 | May 2004 | DE | national |
