ITMI982353A1 - PROCEDURE FOR DETERMINING SLIP IN A CLUTCH PLACED IN THE VEHICLE DRIVE CHAIN. - Google Patents

Description

DESCRIPTION

The invention relates to a method for determining slippage in a clutch arranged in the drive chain of a vehicle.

The clutch, which is arranged between a drive motor and a gearbox in the drive chain of a vehicle, is actuated more and more automatically, as an actuator which operates the clutch is controlled by a control device corresponding to the operating conditions of the vehicle. Automatically operated clutches can also be cascaded to the gearbox. On the one hand, such automated clutches greatly increase the operating comfort of motor vehicles. On the other hand, they contribute to the reduction of consumption, since, in particular in connection with automated gearboxes, one drives more often in a gear favorable for consumption. In this case, the automated clutch is operated in such a way that it is closed only as far as necessary, for reasons of reduced energy consumption of the actuator, reduced expenditure of time for operation and comfort, so that it is closed only when necessary, so that it does not happen. some slippage or some inadmissible high slippage. Knowledge of clutch slip is therefore necessary for many reasons.

If the output speed of the clutch, which is identical to the input speed of the gearbox, is calculated by averaging the speeds of the driven wheels and multiplying by the respective effective overall gear ratio between the input speed of the gearbox and the wheels, then no account is taken of vibrations, which are generated in the drive chain (the drive chain is a system in itself capable of oscillating). The consequence is that a calculation difference, arising in the drive chain due to vibrations, between the measured engine speed (clutch input speed) and the calculated gearbox input speed (engine speed). clutch output) is evaluated as slippage, even if there is actually no slippage present. In order to obtain some certainty with regard to such misinterpretations of slippage, it has hitherto been usual to introduce a fixed slip limit, which must be exceeded in order for the difference in number of revolutions described above to be evaluated as slippage. This slip limit must be set very high in particular in the case of jolting vibrations, such as when driving with very low speed or when starting with a moment jump. In normal running operation this means that slippage is also not recognized even when it is actually present, which can lead to unnecessarily high consumption and a reduction in the life of the clutch.

The invention is based on the task of indicating a method for determining slippage in a clutch arranged between an engine and a gearbox in the drive chain of a vehicle, which makes it possible to recognize slippage occurring in the clutch, without having to be measured the number of clutch output revolutions and this must be considered in case of vibrations of the drive chain.

A first solution of the described aim is characterized in claim 1.

According to the invention, oscillations in the number of revolutions which arise as a consequence of the dynamic behavior of the drive chain are calculated in particular by taking into account the variation of the moment emitted by the motor in the drive chain. In order for the difference between the measured clutch input rpm and the clutch output rpm calculated from the measured vehicle wheel speed and overall gear ratio to be evaluated as slip, this difference must exceed the dynamically calculated speed fluctuations.

Sub-claims 2 and 5 relate to advantageous improvements of the process according to the main claim.

Claim 6 relates to a modified process for solving the aim of the invention. In the case of this procedure, the entire drive chain is reproduced in a mathematical model, which contains measurable state quantities and measurable exciting moments. The clutch output rpm is calculated from the mathematical model. The difference between the measured clutch input rpm and the calculated clutch output rpm is the actual slip in the clutch.

Claim 7 relates to an advantageous improvement of the method according to claim 6.

Furthermore, the invention relates to a device for carrying out a procedure for determining the slippage, in particular according to one of the preceding patent claims.

The invention is illustrated below with the aid of schematic drawings by way of example and in further details.

Figure 1 represents a drive chain of a motor vehicle, Figure 2 represents a vibration pattern of the drive chain,

Figure 3 shows vibrations occurring in the drive chain after a momentary impact,

Figure 4 represents curves to illustrate the determination of the motor moment effective from time to time,

Figure 5 represents the damped vibration of the input speed of the gearbox,

Figure 6 is a flow diagram to illustrate the calculation of the dynamic slip limit,

Figure 7 represents a drive chain similar to Figure 1 with additional sensors,

Figure 8 is a representation to illustrate the determination of the load moment,

Figure 9 is a sequence diagram to illustrate the determination of the input speed of the gearbox,

Figure 10 represents a vibration pattern of the drive chain e

Figure 11 is a vibration pattern of the drive chain.

According to Figure 1, the drive chain of a motor vehicle has a heat engine 2, which is connected by means of a clutch 4 to a gearbox 6, which in turn is connected to the rear wheels 12 by means of a cardan shaft 8 and a differential 10. operated. The front wheels 14 of the motor vehicle are not driven in the example shown.

The clutch 4 is known per se in its structure and contains inter alia a clutch disc 16, which is rotatably connected with the crankshaft of the heat engine 2, a thrust plate 18, which is connected resistant to rotation. rotation with the input shaft of the gearbox 6, and by means of an actuation lever 20 it is released from engagement by friction with the clutch disc 16, overcoming the force of a cup spring.

Gear 6 is a traditional manual gearbox, which is operated by means of a gear lever 22.

An actuator 24, for example an electric stepper motor, is provided for actuating the actuation lever 20, which is controlled by an electronic control device 26.

The electronic control apparatus 26 contains in a per se known manner a microprocessor, memory devices, interfaces, and so on. As input signals, the signals of a speed sensor 28 for detecting the number of revolutions of the clutch disc 16 or the crankshaft of the thermal engine 2 are passed to it, the signals of a position sensor 30 for the detection of the position of the actuator 26 respectively of the operating lever 20, the signals of the wheel speed sensors 32 and 34, as well as possibly further operating parameters of the drive chain, such as the position of a throttle valve of the heat engine 2 and so on. In addition, the speeds of the non-driven front wheels 14 can be passed to the control device 26.

The structure and the operating mode of the plant described up to now are known per se and therefore are not illustrated in more detail.

A difficulty which arises when the number of revolutions of the thrust plate 18, which is equal to the number of revolutions of the input shaft of the gearbox, is calculated by averaging the revolutions of the rear wheels 12 are averaged and multiplying these by the overall transmission ratio of the gearbox 6 and of the differential 10, and then as slippage the difference between the number of revolutions of the thrust plate 18 thus calculated and the number of revolutions of the clutch disc 16 is considered, consisting of the following:

the entire drive chain is a structure capable of vibrating, in which the engine or the combustion engine 2, suspended loosely inside the vehicle, vibrates with respect to the substantially more inert vehicle, which is supported on the ground by the rear wheels 12, where the drive chain acts as an elastic coupling element.

The system capable of vibrating is schematically represented in figure 2. In this case it means the moment of inertia of the engine, i the overall transmission ratio of the gearbox and c the stiffness index of the drive chain.

When the inertia of the motor is excited by a moment jump Δ M, a vibration is formed with the amplitude Δ Μ / c in the proper shaking frequency a ωRuckel. This vibration is represented in figure 3, where on the ordinate there is the number of gi ri n and on the abscissa the time t.

The maximum angular velocity generated as a result of this reduction is calculated as

We have:

Δndyn1 is the speed variation or the maximum speed difference, generated as a result of the motor moment variation ΔΜ. As clutch slip, only the difference between the measured speed of the clutch disc 16 and the input speed of the gearbox or the output speed of the clutch, calculated from the average value of the wheel speeds, is evaluated. rear 12 and of the effective overall gear ratio, is greater than Δ ndyn1.

The shaking frequency ωRuckel depends on the respective gear ratio of the gearbox. Shaking frequencies can be determined based on measurements for each gear, or based on vehicle data. The frequencies for further gear ratios can be determined from the shaking frequency in first gear:

The determination of the motor moment variation Δ Μ is done by comparing the motor moment signal with a filtered motor moment signal. The engine moment signal is measured, for example, because a characteristic range of the engine speed and throttle position or the engine speed and intake pressure is used, from which, in the presence of quantities date, the engine moment is read. Similarly, the motor moment can also be obtained directly from the motor control, as for example via a data bus, such as a CAN bus. A filtered engine moment signal is derived from the engine moment signal, since the engine moment signal passes through a filter with a filter time constant Tp in a known manner. The filter time constant Tp should not be chosen too small, as otherwise the filtered signal follows the raw signal too quickly and no precise determination of the motor moment change ΔΜ is possible. A filter time constant Tp is appropriate, which corresponds to double the duration of the period of the shaking vibration. A determination of Δ Μ can be made from the motor moment values stored for this purpose at previous time instants.

Figure 4 shows two representations, the upper of which represents the difference between the motor moment signal Mp and the filtered motor moment signal ME F. The lower curves are identical to the upper curves and show the filter time constant TF; the shorter the filter time constant TF, the faster the filtered moment signal ME F approaches the actual motor moment ΜE. A temporal decrease in the vibration of the drive chain is described by determining the moment change Δ Μ by comparing the jump signal ME with the filtered ME signal F.

As a result of damping in the drive chain, the amplitude Δn of the shaking vibration decreases over time. The procedure described above, that is to describe the decrease in vibration by means of the time decrease of ΔΜ, is generally not sufficiently precise. For this reason, the amplitude for the next time step is determined from the amplitude of the shaking vibration, in which the decrease in vibration is taken into account with the damping constants D. For the new amplitude we have:

During a period of the shaking vibration, the command is called p times or the speed is read p times, so that for the decrease constant k (decrease constant for each command interruption) it results:

For a simplified calculation of k the upper term is subjected to a series development. Therefore it is true for example in a first approximation:

where further elements of series development can also be used, when accuracy needs to be increased.

Therefore for the dynamic slip limit, from the damping influence we have:

In this way, two parts are available for determining the slip limit, i.e. on the one hand the slip limit Δndynl calculated from the motor moment variation Δ Μ and on the other hand the slip limit Δ ndyn2 calculated on the basis of the damping influence, where the maximum value of both parts is used as the slip limit:

In contrast to the state of the art, in which a fixed, set very high slip limit is used to suppress the influence of vibrations in the drive chain, the invention makes it possible to work with a realistic slip limit adapted to the actual vibrations of the drive chain.

Figure 6 represents the illustrated procedure for determining the slip as a sequence diagram:

In step 100, the slip Δn is calculated in the conventional way due to the fact that the input speed of the gearbox determined by the measured wheel speeds and the overall gear ratio is subtracted from the measured engine speed.

In step 102, the motor moment variation ΔΜ is calculated, as illustrated on the basis of Figure 4.

In step 104 the slip limit Δndynl is calculated from the motor moment variation ΔΜ according to formula (1).

In step 106 the slip limit Δndyn2 is calculated from the damping influence according to formula (2).

In step 108 it is determined whether Δndynl is greater than Δndyn2. If so, in step 110 it is determined that Δη ^ η1 is the value of the dynamic Δndyn slip limit. If not, in step 112 it is determined that Δndyn2 forms the dynamic Δndyn slip limit. In step 114 it is then established whether the slip Δη determined in the conventional way is greater than Δndyn. If so, this is evaluated as the generation of slippage on the clutch. If this is not the case, this is evaluated in the sense that no slippage is generated on the clutch.

As an alternative to the method described above, there is the possibility of reconstructing at least approximately from measured quantities the entire state vector of the dynamic "drive chain" system. For this purpose, the mathematical reproduction of the drive chain based on its dynamic model is fed with the input quantities of the motor moment and load ML, and a comparison of the measured quantities with the corresponding quantities of the mathematical model is performed. For this purpose, the difference between the measured quantities of the drive chain and the quantities determined by the mathematical model is linked (observed) with an appropriate weighting at the input of the mathematical model. The mathematical model is therefore so excited that it vibrates in synchrony with the drive chain. In this way, non-measurable quantities can be taken from the mathematical model. In the particular case of the slip determination, the non-measurable quantity of the gearbox input speed or the clutch output speed is taken from the mathematical model and compared with the measured engine speed. With the help of this comparison it can be determined whether slippage is present or not.

Figure 7 shows an actuation chain which corresponds to that of Figure 1, but is equipped with additional sensors, such as the position sensor of the throttle valve 36, the speed sensor of the cardan shaft 38 and so on. These additional sensors are also connected to the electronic control apparatus 26, within which the mathematical model is stored.

In the case of the calculation procedure described above by means of an observer, it is problematic that in the specific case of the motor vehicle, the load moment ML (running resistance, slope, etc.) is unknown. It is therefore necessary to determine the load moment ML by means of an estimate of the disturbance quantities. Measurable variables such as travel speed (from wheel speeds) and engine speed can be used for this. In the case of wheel speeds, the speeds of the front wheels 14 are also advantageously taken into account, which generally does not mean any effort, since these speeds are detected with the aid of ABS sensors which are certainly present. With the known inertia of the engine and the vehicle, on the basis of a highly simplified model, which is represented in figure 8, an estimate quantity for the load moment ML can be determined:

We have:

where: is the moment of inertia of the engine, JKFZ the mass moment of inertia, reduced on the side of the engine, of the vehicle, is the speed of rotation of the engine, ωKFZ is the speed of rotation of the vehicle projected on the side of the engine.

The dynamic mathematical model of the motor vehicle can be represented as follows in the form of a state:

where the vector x brings together the state quantities (angle of torsion, angular velocities) and the vector u the exciting moments (motor moment, load moment). The system is described by the state matrix A. Using the control matrix B, the individual exciting moments are prefixed to the individual state coordinates.

Figure 9 shows a flow diagram for the illustrated determination of the slip from a complete mathematical model. The moment input quantity of the engine, which is measured (for example from the stress of the bearings, which support the engine on the vehicle) or calculated (for example from the number of revolutions and angle of the throttle valve or from information from the engine control), it acts on the motor vehicle 120. On the motor vehicle 120, with the aid of sensors, (122) measurement quantities are determined. In addition, the load moment is determined, as illustrated with the help of Figure 8 (124). The load moment and the motor moment are entered (126) in a dynamic vehicle model as input quantities. From the dynamic vehicle model (126) the measured quantities (122) are read out (128) mathematically. The difference between the mathematically determined measured variables (128) and the directly measured measured variables is dynamically weighed (130) and entered in the dynamic model (126). By means of a suitable choice of dynamic weighing, the dynamic model is energized in such a way that it vibrates in conjunction with the vehicle, so that the input speed of the gearbox or the output speed of the clutch can be calculated and compared with the number of engine revolutions respectively the number of clutch input revolutions. On the basis of this comparison, the slip of the clutch can therefore be calculated directly.

As an example for the model formation the following is represented: for the case of the slipping clutch, according to figure 10 we have:

With the known inertia of the engine 201, of the gearbox 203 and of the vehicle 205 and of the clutch 202 with its transmissible torque, as well as with the rigidity of the drive chain 204, with the aid of the model of figure 10 the dynamic vehicle model:

With the state vector x the command vector u, the state matrix A and the command matrix B we have:

In a further example of FIG. 11, a model can be prepared for the case of the non-slipping clutch. In this case the angles of rotation of the clutch inlet and clutch outlet are identical. Therefore, the inertia of engine and gearbox rotation can be combined. We have:

With the state vector x, the command vector u, the state matrix A and the command matrix B we have:

Basically, a method according to the invention and a device for carrying out the method are described, with which the slip, calculated from the difference between the number of revolutions of the engine and the number of revolutions of motion of the gearbox or at least of individual wheels of the vehicle, it can be distinguished between slippage actually present on the clutch and a virtual slippage as a difference in number of revolutions, which results from the dynamics of the transmission path (torsional vibrations of the drive shaft between gearbox and vehicle wheels) between input gearbox and wheel.

If vehicle reactions or clutch operations are initiated, which are performed as a function of slipping, in the event of real slipping on the clutch, the vehicle reaction or clutch operation may be initiated, which can be prevented in the event of virtual slipping. For example, the control / adjustment contains a part, which leads to the closing of the clutch if slippage is recognized.

In suitable driving situations of the vehicle, slippage of the clutch may be present, which therefore involves closing, according to the command, of the clutch. On the other hand, for example due to repeatedly initiated load changes, a virtual slip can be achieved as a difference in speed between the input speed of the gearbox and the drive speed weighted with the gear ratio. overall transmission.

As a further example, a temperature model / load or stress model for determining the clutch temperature / clutch stress is implemented in the control / adjustment of the clutch which can be operated automatically. With the help of vehicle data, the temperature of the clutch or the frictional power introduced into the clutch is calculated. According to the control, defined reactions take place in the vehicle or when the clutch is actuated when a limit temperature / limit stress is exceeded. The control based on the determination and differentiation between slip and virtual slip can control starting or preventing changes in the clutch actuation.

In the case of a method for determining slippage in a clutch, the clutch input speed or the engine speed is measured, and the clutch output speed is calculated by measuring the speed of at least one vehicle wheel and the overall effective transmission ratio between the clutch output and the vehicle wheel. In the case of a first embodiment of the procedure, with the aid of a mathematical model, which describes the dynamic behavior of the drive chain, oscillations of the number of revolutions Δndyn are calculated, which result as a function of variations in the operating parameters of the drive chain, and are evaluated as slippage, when it has

The invention also relates to a device for determining slippage corresponding to what has been described above.

The patent claims filed with the application are proposed for formulation without prejudice to obtaining further patent protection. The Applicant reserves the right to claim still further characteristics disclosed so far only in the description and / or in the drawings.

The references used in the sub-claims refer to the further implementation of the subject matter of the main claims by means of the characteristics of the respective sub-claim; they are not to be understood as a waiver of obtaining autonomous objective protection for the characteristics of the sub-claims containing the references.

However, the objects of these sub-claims also form autonomous inventions, which have a configuration independent of the objects of the preceding claims.

Furthermore, the invention is not limited to the exemplary embodiments of the description. On the other hand, numerous variations and modifications are possible within the scope of the invention, in particular of variants, elements and combinations and / or materials, which are inventive for example by combining or modifying individual characteristics or elements or process steps, described in connection with the general description and the embodiments as well as the claims and contained in the drawings, and by means of combinable characteristics lead to a new object or to new process steps or sequences of process steps, including with regard to manufacturing, testing and working processes .

Claims (8)

CLAIMS 1. Method for determining slippage in a clutch arranged between an engine and a gearbox in the drive chain of a vehicle, in which method the input speed of the clutch nKi and the output speed of the clutch are measured. nKa clutch is calculated by measuring the number of revolutions of at least one wheel of the vehicle and by the overall transmission ratio, effective between the clutch output and the vehicle wheel, characterized by the fact that with the aid of a mathematical model, which describes the dynamic behavior of the drive chain, speed oscillations Δ ndyn are calculated, which result as a function of variations in the operating parameters of the drive chain and is evaluated as slippage when there is Method according to claim 1, characterized in that the oscillation of the speed Δndyn is determined with the aid of the following formula where we have: ΔΜ = variation of the motor moment, = motor moment of inertia and fR = shaking frequency. Method according to claim 2, characterized in that the motor moment variation ΔΜ is determined by comparing a motor moment signal with a filtered motor moment signal. 4. Process according to claim 1, characterized in the fact that the oscillation of number of revolutions Δndyn is determined according to the following formula: where we have: with D = damping constant of the shaking vibration and TR = time duration of a shaking vibration. Method according to claims 4 and 2, characterized in that the speed fluctuation Δndyn is the greater of Δndynl and Δndyn2 · 6. Method for determining slippage in a clutch arranged between the engine and a gearbox in the drive chain of a vehicle, in which the method of measuring the clutch input speed or the engine speed nKi, and the number of output revolutions of the clutch nKa is calculated with the aid of the measurement of at least one number of wheel revolutions, characterized by the fact that the entire drive chain is reproduced in a mathematical model of the following form, where x are the state quantities, u the exciting moments, A the state matrix and B the command matrix of the drive chain, and the number of clutch output revolutions is calculated with the aid of the mathematical model. 7. Process according to claim 6; characterized by the fact that the load moment (ML) acting from the outside on the drive chain is calculated according to the following formula: where we have: ME = engine moment, JM = engine moment of inertia, ωM = angular speed of the engine, = total moment of inertia on the vehicle wheels, ωKFZ = angular speed of the vehicle wheels. 8. Device in particular for carrying out a method according to the preceding claims.