DE19546651A1 - Continuously variable transmission vehicle driving method - Google Patents

Abstract

The continuously variable transmission includes a driving mode in which the driver selects the maximum engine speed and the transmission selects the gear ratio to match this maximum speed. this provides increased torque control for special purposes. The maximum selected speed is at a set level below the set engine maximum. The transmission ratio is set in relation to the motor speed regulating control. The system includes a torque enhancement mode ie. a kick-down mode when required. If the selected maximum engine speed is exceeded by more than a set amount the control adjusts the transmission ratio to reduce the engine speed.

Description

The use of a continuously variable transmission allows it, the vehicle in the optimal area of the drive to operate motors. Especially for vehicles with Ver combustion engine offers the use of infinitely adjustable Gears, especially the use of types with high Efficiencies in the low load range have great advantages visually the pollutant emission and with regard to the force fabric consumption.

For practical use, driveability plays a role the response to acceleration requests as well like the maximum torque that can be generated at the final drive special role. In particular, achieving a maximum Torque on the axle drive is for market acceptance important, especially with short-term full load requirements by the driver (kick-down) to the Driving speed adjusted low translation ratio Ratio of the transmission is set and the engine operated at correspondingly high speeds with high performance can be used. The problem here is that the like operating points the engine speed limitation control responds and the transmission is controlled so that an unfavorable engine operating point occurs.

The invention has for its object an operating procedure ren to create that the demands on driveability, Fahrkom continued and responsiveness is sufficient.

According to the invention, this object is achieved by a method to operate a vehicle with continuously adjustable rem transmission, especially a vehicle with combustion engine in which the gearbox is controlled by the driver's request  Gear ratio is controlled so that the engine at the highest possible speed, preferably a predetermined one Nominal speed, works.

In the following explanations of the invention means the term "limit speed" means the speed of the motor, the may not be exceeded for safety reasons. The term "nominal speed" means the speed that the Distance is below the limit speed and at which the Engine delivers the maximum possible power and thus the for the most economical performance to be achieved point represents. The term "highest possible speed" means a specifiable speed, which in the respective operation depending on the driver's request and depending on the given operating situation also the Nominal speed, the limit speed or a speed short below the nominal speed.

The method according to the invention enables control of speed and gear ratio in such a way that the gear ratio according to the driver's request is set that the engine is always in the cheapest mode point works. This also ensures that a rotation number limitation to the specified limit speed your own Liche protective function is maintained because by the specification of Nominal speed as an optimal operating point is always sufficient the distance to the limit speed is maintained.

In an expedient embodiment of the invention, that the control of the gear ratio via a Engine speed controller takes place, which is the engine speed for the given driver request for the highest possible speed upregulated. This makes it suitable for practically all load ranges operating the engine at the optimum operating point accomplishes. It is expediently provided that the through highest engine speed that can be set by the engine speed controller maintains a distance from a predetermined limit speed, so that over-revving of the engine is avoided in any case.  

In a further embodiment of the invention, that with a full load request a given driving speed of the vehicle at the time of full load requirement adjusted gear ratio and at least until the predetermined maximum is reached possible speed is observed. Through this operating wise it is assured that from every driving speed out by the driver through a kick-down accordingly low gear ratio is controlled that operating the engine at high speeds and at high speeds Performance guaranteed.

In one embodiment of the method according to the invention provided that when the predetermined highest possible engine speed, preferably the nominal speed, by a predetermined amount in the direction of the predetermined Limit the gearbox control requirement in the direction is maintained on a long translation for so long until the engine speed reaches the specified highest engine speed number has dropped again. This measure is safe asked that due to the increasing load, the speed drops again to the specified highest engine speed. If the specified maximum engine speed is exceeded number, for example the nominal speed, and if the gearbox setting not yet specified for the longest translation is what is possible with dynamic processes the remaining requirement for the transmission control in Towards a longer translation upright for so long hold until the engine speed returns to the nominal speed has fallen behind.

The invention is explained in more detail with reference to drawings. Show it:  

Fig. 1, the dependencies of the different para meters at full load,

Fig. 2 is a block diagram of the principles of the procedure,

Fig. 3 is a block diagram for a complete engine control for performing the United method.

In Fig. 1, the specific engine torque M / M _max in relation to the specific speed v / v _{max is} shown in diagram 1.1 .

Diagram 1.2 shows the speed as a function of the specific speed v / v _max in the assignment to diagram 1.1 .

The diagram 1.3 shows in a corresponding assignment the gear ratio i as a function of the specific speed v / v _max .

Diagram 1.4 shows the specific power P / P _nominal as a function of the specific speed v / v _max .

If the driver specifies the desire for the highest possible acceleration, the translation according to Diagram 1.3 is selected so that the maximum possible performance results. At low speed, the shortest possible ratio i _{max is} activated (curve area 1 ), as shown in Diagram 1.3 . As can be seen in diagram 1.2 , the engine speed (curve area 2 ) increases until the specified nominal speed 3 is reached.

As can be seen in the assigned diagram 1.1 , due to the constant gear ratio, there is an increasing torque curve in the output torque (area 4 ), whereby the engine power and thus also the output power, apart from gearbox losses, increases steeply, as shown in the diagram 1.4 can be seen.

When the specified nominal speed 3 is reached , i.e. the speed at which the engine delivers the maximum power, as can be seen in Diagram 1.3 , the gear ratio is shifted towards a longer gear ratio to lower values of i. As will be explained below, the translation is controlled via an engine speed controller, which adjusts the engine speed to the predetermined nominal speed. It is hereby achieved that with increasing speed the full engine power is still available until the nominal maximum speed is reached. When the nominal maximum speed is reached, the transmission has reached its longest possible transmission ratio i _min . Above the nominal maximum speed, the engine speed continues to increase due to the constant gear ratio (range 6 ), while the engine power (range 7 ) and correspondingly the output torque (range 8 ) drops sharply. Driving above the nominal maximum speed can only be achieved when driving on downhill and / or tailwind roads.

Fig. 2 shows a block diagram of the sequence of the control method.

The vehicle is shown schematically here by its motor 10 , which acts on the road 14 via a continuously variable transmission 11 , the axle transmission 12 and the drive wheels 13 .

The engine load specification is predefined, for example, via an accelerator pedal 15 provided with corresponding sensors and, depending on the equipment of the engine, can be adjusted via an adjustable throttle valve or alternatively with throttle-free load control, as is possible with diesel engines or engines with fully variable valve trains, for example electromagnetic valve drives Engine management system 17 take place. In the following description, the control of a throttle valve 16 is described for the sake of simplicity. However, reference numeral 16 basically stands for load control.

The throttle valve 16 of the engine 10 is controlled via the engine management system 17 by the accelerator pedal 15 via an upstream drive train management system 18 . Direct control via the drive train management system is also possible.

The continuously variable transmission 11 is assigned a transmission management system 19 , to which information about the transmission ratio to be set is predetermined by the drive train management system 18 . In accordance with this requirement, the transmission ratio system 19 controls the corresponding transmission ratio on the transmission 11 .

The drive train management system is fed by means of a speed sensor 20, the respective actual value of the engine speed. The actual value of the actual driving speed is transmitted to the drive train management system 18 via a sensor for determining the actual driving speed, which can be designed, for example, as an output speed sensor 21 on the transmission.

For example, if the throttle valve 16 is fully opened when the driver requests "maximum acceleration" or, in the case of an engine with fully variable valve trains, the valve trains are appropriately controlled via the engine management system and the transmission is set to the shortest possible translation, ie i _max , via the transmission management system 19 , then an appropriate one is set Control loop queried via the speed sensor 20, the actual value of the engine speed.

If it is found here that the actual value of the engine speed is higher than a predetermined nominal speed, the gear 11 is set in the direction of a longer transmission ratio, that is to say toward a larger i. This increases the load on the motor 10 and the speed decreases again.

If the actual value of the rotational speed determined by the rotational speed sensor 20 is less than the predetermined nominal rotational speed, then the transmission management system 19 adjusts the translation on the transmission 11 to shorter gear ratios, that is to say to a lower i. This reduces the load on the motor and the speed can increase again to the specified nominal speed.

Only when the specified nominal speed is significantly exceeded does the speed limitation of the motor become effective via a control circuit (not shown). If, via the transmission management system 19, the transmission 11 had not yet been adjusted to the longest possible gear ratio, which is possible in dynamic processes, the requirement to control the gear 10 in the direction of longer gear ratios is maintained until the speed again reaches the predetermined nominal speed has dropped. The corresponding controller can be designed according to customary criteria, for example as a PID controller, in which the positive and negative PID components can be separated but can also be adjusted progressively.

Fig. 3 shows in a further block diagram a fully permanent control for performing the method. The gear ratio is represented by the parameter r, as it results from the addition of the axle ratio.

The drive train management system 18 here has an adaptation block 22 in which the driver's request specified by the accelerator pedal 15 is converted into a road load request M _s , which is linked to a block 23 for converting the target road torque M _s into a target engine torque M _mot . With block 23 , block 24 is still linked, in which the required position of throttle valve 16 is determined.

In this arrangement, the transmission management system 19 has a block 25 for determining the cheapest transmission ratio R _s , to which a PID controller 26 is assigned, via which an adjustment of the transmission 11 to the desired transmission ratio is effected.

The function of the individual blocks and the others Switching elements shown is in detail below explained in more detail.

The adaptation block 22 is, as already shown with reference to FIG. 2, the engine speed n in each case via the speed sensor 20 and the current speed v is fed via the sensor 21 as a further input parameter. The road load requirement stipulated by the accelerator pedal 15 is implemented, for example, as a formula or, as indicated in the figure, implemented via a characteristic curve or a multi-dimensional map, in order to ensure a more comfortable driving behavior. A "normal" accelerator pedal can also be simulated via the adaptation block 22 , or the respective accelerator pedal position can also be assigned to a specific acceleration or deceleration request. Also in the event of a deceleration request, a speed dependency is preferably provided, since with the driving speed v = 0, no deceleration is certainly desired and the driver expects that acceleration will occur even with a slight actuation of the accelerator pedal.

The target road torque M _s generated by the adaptation block 22 is now passed on the one hand to the block 23 and converted there into a target engine torque M _mot , for example according to the formula M _mot = M _s / r, the total transmission ratio of the drive being represented by the variable r.

On the other hand, the signal M _{s is} fed to block 25 , which determines the cheapest transmission ratio r _s on the basis of a corresponding map. In this map, the most favorable values for the respective torque / speed combination are stored, the values also being able to be determined in such a way that compliance with emission limit values in the exhaust gas are possible with the lowest possible fuel consumption. Also in the case of the maximum load requirement by the driver, for example for the kick-down, the characteristic diagram, the characteristic curve shown in FIG. 1 in diagram 1.3 , can be stored in the characteristic diagram of block 25 .

The target gear ratio r _s derived therefrom is next transferred to a PID controller 26 , which causes the gear 11 to be adjusted to the desired gear ratio. The transmission 11 includes an encoder 27, by which the actual transmission behaves nis _r can be tapped. The signal of the actual transmission ratio r given by the encoder 27 _is fed to the PID controller 26 , via which a corresponding de-adjustment takes place.

Furthermore, the signal r _{is made available to} the block 23 for calculating the required engine torque via the encoder 27 . This link creates a favorable dynamic behavior. However, it is also possible to apply the signal r _s obtained in block 25 directly to block 23 .

From the value obtained in block 23 for the engine torque, the required position of the throttle valve 16 can now be calculated or, in the case of an engine with throttle-free load control, corresponding quantities such as valve control number or injection duration can be calculated. These calculation steps take place in block 24 . In the case of the throttle valve control, further values measured on the engine 10 are required to determine the required angle a _DK , in particular the engine speed n, the ambient or intake manifold or boost pressure P _u and intake air temperature. This data to be tapped from the engine is symbolized by the signal strand 28 between the engine and block 24 . The formal connection need not be described here, since it is known. In the presence of combustion chamber pressure sensors or torque sensors, the engine can even be regulated loudly to a target value. However, this is not shown in the block diagram here for reasons of clarity.

The engine speed n is of great importance in the regulation for realizing the maximum acceleration. The engine speed n tapped at the engine by the speed sensor 20 is fed to a further PID controller 29 which, when the full load request is present, determines a correction value for the target value of the transmission ratio which is dependent on the current engine speed and which is in a summation element 30 of the im Block 25 determined target value r _{s is} subtracted. The limitation to the permissible maximum speed then takes place independently of this in block 29 . However, this correction value can be used to influence the engine load control, especially when a certain size is exceeded.

The maps or equations contained in block 22 and block 25 can also be expediently laid out adaptively. So the vehicle behavior can be adapted to the driving way. For example, a corresponding preselection can be used to choose between a sporty and a consumption-friendly behavior. Either the system is reconfigured by switching or by manually setting a parameter, or the system is automatically adapted to the driving style using assessment criteria such as accelerator pedal dynamics, lateral forces or similar additional parameters.

For example, a particularly economical one Achieve adjustment when the gear is as long as possible gear ratios can be selected and the engine always included operated relatively low speeds and high moments becomes. On the other hand, if one meets the requirements of Maximum acceleration similar gear ratio too chosen for the normal case, then results with regard to the dynamics a much more favorable driving behavior, because not in the event of a sudden acceleration request only the slow transmission adjustment must take effect but only open the throttle valve fully the valve control must or via the engine management system must be adjusted accordingly, what is within seconds fractions can be realized.

The assignment of the individual blocks or modules made in FIG. 3 to the unit "engine management system", "drive train management system" or "transmission management system" is given here with regard to the assignment to the block diagram in accordance with FIG. Fig. 2 takes place. Because all systems are networked, there is no strict division. For example, the PID controller 29 can be assigned to either the engine management system 18 or the transmission management system 19 .

Claims (5)

1. Method of operating a vehicle with stepless adjustable gear, especially vehicle with scorching motor, controlled by the driver's request Gear ratio is controlled so that the Motor with the highest possible speed, preferably one specified nominal speed works. 2. The method according to claim 1, characterized in that the control of the gear ratio via a motor speed controller takes place, which is the engine speed for the opposite adjusts the driver request to the highest possible speed. 3. The method according to claim 1 or 2, characterized in that the highest adjustable by the engine speed controller Engine speed a distance to a predetermined limit speed number complies. 4. The method according to any one of claims 1 to 3, characterized characterized in that at a full load request the current driving speed of the vehicle at the time gear ratio adapted to the full load requirement controlled and at least until reaching the previous given the highest possible engine speed. 5. The method according to any one of claims 1 to 4, characterized characterized in that when the specified the highest possible engine speed by a predetermined Measure in the direction of the specified limit speed Transmission control requirement towards a long Gear ratio is maintained until the engine speed to the specified highest engine speed again has dropped.