AT517108B1 - METHOD FOR OPERATING VEHICLES OPERATED VIA A DRIVE MACHINE AND A DRIVE TRAIN WITH AT LEAST ONE COUPLING OPERATED VEHICLE - Google Patents

Abstract

The invention relates to a method for operating a vehicle operable via a drive machine and a drive train with at least one clutch, wherein the vehicle is at least temporarily operated in a creep mode with slipping clutch, wherein an output speed (n2) on the clutch output side with slipping clutch different a drive speed (n1) on the clutch drive side, and wherein - when the output speed (n2) or the vehicle speed exceeds a defined threshold - the clutch slip torque (trq) is changed at least temporarily. To increase the ride comfort, it is provided that a controller for setting a target slip speed is activated when the output speed (n2) reaches or exceeds a synchronous speed (ns) of the clutch, the clutch also slips when transmitting negative engine torque and the Transition from negative engine torque to positive engine torque with minimum transmitted clutch torque (trq0).

Description

The invention relates to a method for operating a vehicle operable via a drive machine and a drive train with at least one clutch, wherein the vehicle is at least temporarily operated in a creep mode with slipping clutch, in which an output speed on the clutch output side with slipping clutch different to a drive speed on the clutch drive side, and wherein - when the output speed or the vehicle speed exceeds a defined threshold - the clutch torque is changed at least temporarily.

During a creep mode, especially on downhill roads, the vehicle speed may exceed the defined target speed for creep, typically the target speed for creep is below the speed at which the clutch would be synchronized.

This exceeding of the target creeping speed is not desired, whereby countermeasures must be taken. The first countermeasure in this invention is the prior art - when the target creep speed is exceeded, the clutch torque is reduced (possibly to 0) to not actively accelerate the vehicle further. If the output speed of the clutch in this state nevertheless reaches a speed close to the drive speed due to the gradient, this is typically referred to as "run away" and the type of countermeasure changes.

From the prior art, it is known to close the clutch when a "run away" of the vehicle is detected in order to achieve an engine braking effect and to prepare the exit from the creep function to a driving mode with a closed clutch.

Typically, the clutch closes close to the synchronous speed and so it may occur that the engine speed is recalculated above the output speed to the input shaft when the clutch closes. If so, torque is transferred from the engine to the drive wheels, with the engine idle speed control providing that torque. However, this is undesirable because it means that the vehicle is being accelerated by this extra moment. Once the output speed recalculated to the input shaft exceeds the idle speed of the engine, the engine idle controller reduces the torque to a negative torque on the clutch input side which is transmitted to the wheels. This is the second countermeasure against the vehicle acceleration and thus the vehicle is trying to slow down by the engine braking effect.

If the clutch is closed and changes the sign of the torque request from a positive engine torque to reach the idle speed to a negative moment to reduce the idle speed, so this load change in handling, depending on the idle controller tuning, as a jerk noticeable. If the slope changes again after this event and eventually even becomes a slight incline, the actual speed achieved during creeping is not equal to the target creep speed, because in this case the clutch has already been closed and the creep condition has been left. The vehicle speed then corresponds to the idle speed of the engine to which this adjusts.

The object of the invention is to avoid the disadvantages mentioned and to increase the ride comfort.

According to the invention this is achieved in that a controller for setting a target slip speed is switched active when the output speed reaches or exceeds a synchronous speed of the clutch, wherein the clutch also slips when transmitting negative engine torque and the transition from negative engine torque to positive Engine torque at minimum transmitted clutch torque occurs.

By measuring the output speed on the clutch output side or the vehicle speed is determined whether a target value for the output speed or vehicle speed is exceeded in creep mode. Increasing the output speed or the vehicle speed can be done for example by a sloping road or other external influences acting on the vehicle.

Just as in the prior art, the clutch torque is reduced as the first countermeasure to not further accelerate the vehicle. To reduce the clutch torque, the clutch pressure is reduced, so the clutch is opened.

By reducing the clutch torque transmitted from the engine to the drive wheels of the vehicle drive torque is reduced.

If the output speed and thus the vehicle speed now increases despite the reduced to the minimum value clutch torque (possibly 0), the clutch remains in this state until the output speed of the synchronous speed and the vehicle speed corresponds to the synchronous vehicle speed. The synchronous speed is the speed on the output side of the clutch, which is equal to the speed on the input side of the clutch and whereby a torque-free engagement is enabled. The same applies to the synchronous vehicle speed.

As a second countermeasure, upon reaching the synchronous speed of the clutch, or when the synchronous speed plus offset, which takes place at minimum clutch torque, a controller is actively switched, which is to set a target slip speed. This target slip speed is defined so that the speed of the clutch input side, so the engine speed is less than the speed of the clutch output side proportional to the vehicle speed - this is referred to as negative slip. Since this slip is not reached when the synchronous speed is reached, the controller keeps the clutch at the minimum possible clutch torque. A particularly high level of ride comfort is achieved by the fact that the clutch also slips when transmitting negative engine torque and the transition from negative engine torque to positive engine torque always occurs at minimum transmitted clutch torque.

It is particularly advantageous if the target slip speed is reduced with increasing vehicle speed, because it is, if it is not possible to slow the vehicle by the negative engine torque, to a smooth engagement and thus to a smooth transition to normal ferry service. If the clutch torque, which the controller adjusts, is sufficient to reduce the vehicle speed due to the negative engine torque, the clutch torque is reduced again by the controller and the synchronous speed with minimum clutch torque passes. Only when the output speed or the vehicle speed drops to or below the defined target creep speed, the clutch torque increases again and the regular creep tried to regulate to this speed.

However, if the negative clutch torque is insufficient to reduce the vehicle speed, then the output speed or vehicle speed will continue to increase. In this case, the controller typically increases the clutch torque to set the desired slip speed.

The limitation of the maximum transmitted via the clutch braking torque is given by the maximum possible negative torque of the engine.

The invention will be explained in more detail below with reference to the non-limiting figures.

Fig. 1 shows a speed curve and Fig. 2 shows a torque curve of the drive train of the vehicle when using the method according to the invention.

In Fig. 1, the speed n is plotted against the time t, wherein with n1L the idling speed of the prime mover, with the current speed of the prime mover and with n2 the output speed on the output side of the clutch, are designated. Furthermore, a first limit nGi for the

Beginning of the RunAway function and a second limit value nG2 drawn for ending Run Away function. The beginning of the Run Away function is designated RA1, the end of the Run Away function is RA2.

Fig. 2 shows the course of the clutch torque trq during the inventive method.

The creep function generally attempts to achieve a target value n2z for the output speed n2 during the creep mode, which is below the synchronous speed ns corresponding to the idling speed n1L.

During a creep mode, it can happen, in particular on a steep road, that the vehicle speed increases and the output speed n2 exceeds the target speed n2z or the vehicle speed exceeds the target creep speed.

If the output speed n2 exceeds the defined target value n2z for the output speed and approaches the synchronous speed ns, the clutch torque trq is reduced in step A. This is to ensure that the vehicle is not further accelerated by the prime mover. If, nevertheless, the synchronous speed ns is reached (designated B in the figures), then the requested clutch torque, which the controller adjusts, is at the latest at this time at a minimum value (trq0) - see phase C.

Once the output speed n2 reaches the first limit nGi, which is above the synchronous speed ns, "Run-Away" is detected and controlled the clutch torque to hold the clutch to a defined negative slip, the drive speed of the prime mover is smaller Thus, torque is transmitted from the drive wheels of the vehicle to the prime mover to the prime mover at the phase indicated by D in Figures 1 and 2. The prime mover consumes torque, thereby attempting to decelerate the vehicle Sign change of the idle control of the engine for the vehicle occupants not noticeable, since at the time at which the power flow reverses, no significant torque is transmitted through the clutch.

If the vehicle is sufficiently decelerated by the braking torque of the prime mover and then changes the road gradient, the method for inhibiting the "Run Away" is terminated as soon as the vehicle speed or the output speed n2 falls below a second threshold nG2, which is above the idle speed n1L of the prime mover.

If the braking torque of the engine during the negative slip control of the clutch is not sufficient to decelerate the vehicle and the vehicle speed continues to increase, the target slip trqz is reduced at the clutch with increasing vehicle speed. At a parameterizable threshold, the target slip is reduced to 0, whereby the clutch is completely closed by the control. Subsequently, the creep mode is left and a drive mode is activated with the clutch fully engaged.

In the case shown in Figs. 1 and 2, the braking torque of the engine is sufficient to reduce the vehicle speed and the creep mode is not terminated. First, in phase A, the vehicle speed or the output speed n2 rises above the target value for the vehicle speed or output speed n2z. The clutch torque is reduced to a minimum torque trq0 by the control to the target speed n2z at the latest when the synchronous speed ns is reached at 0 Nm) must be reduced. Subsequently, in phase C, the vehicle speed or the output speed n2 rises above the synchronous vehicle speed or synchronous speed ns, but the clutch remains open. As soon as the vehicle speed or the output rotational speed n2 exceeds the first limit value nGi, the functionality of the deceleration of the drive train by the drive engine is activated and attempts to regulate the clutch to a negative slip. For this purpose, the clutch pressure is gradually increased, whereby more torque is transmitted to the engine and its speed ni increases, so that the required slip can be achieved. Subsequently, the vehicle speed or the output speed n2 decreases and the prime mover reaches its idling speed n1L (phase D). The clutch is now opened again by the control so that it is open when n1L (idle speed) passes through the output speed n2 or transmits only a minimum torque trq0 (phase E). When the vehicle speed n2 falls below the second limit nG2, the drive train decelerating operation is stopped by the prime mover, and the creep mode is continued (phase F). In creep mode, it is attempted to keep the target creep speed or target speed n2z.

No jerk is felt when the sign of the torque control of the drive machine changes, since at this time no or only a minimum torque is transmitted via the clutch.

The functionality of the deceleration of the drive train by the prime mover is activated only after the synchronous speed ns has been exceeded, therefore, the clutch is open at this time. By increasing the torque of the clutch only after exceeding the synchronous speed ns, no torque is supplied from the prime mover to the wheels. In this case, the clutch is closed later than in conventional creep functions and operated previously controlled over a certain speed range to negative slip. The advantage over prior art features is that no torque is transmitted from the prime mover to the wheels by closing the clutch at n2 near n1L.

Due to the control on a negative slip on the clutch this slipping until either the target slip is reduced to 0 (high vehicle speed, leaving the creep mode) or the functionality of the deceleration of the drive train is left by the prime mover and the creep mode with the Regulation is continued to the target creeping speed.

The inventive method is suitable for all drive trains with automated transmissions with starting clutch, which have a creep mode.

Claims (5)

claims A method of operating a vehicle operable via a prime mover and a drive train with at least one clutch, wherein the vehicle is at least temporarily operated in a creep mode with a slipping clutch, wherein an output speed (n2) on the clutch output side with slipping clutch different from a drive speed (ni) on the clutch drive side, and wherein - when the output speed (n2) or the vehicle speed exceeds a defined threshold - the clutch slip torque (trq) is at least temporarily changed, characterized in that a controller for setting a target slip speed is switched active, when the output speed (n2) reaches or exceeds a synchronous speed (ns) of the clutch, the clutch also slips when transmitting negative engine torques and the transition from negative engine torque to positive engine torque in both directions with minimum transmission Clutch torque (trq0) takes place. 2. The method according to claim 1, characterized in that the target slip speed is reduced with increasing vehicle speed. 3. The method of claim 1 or 2, characterized in that the target slip speed is selected so that the clutch output side has a higher speed than the clutch drive side. 4. The method according to any one of claims 1 to 3, characterized in that - when the output speed (n2) or the vehicle speed decreases a - the amount of the clutch torque (trq) is reduced, wherein preferably the clutch torque (trq) at passage of the synchronous speed (ns) becomes minimal. 5. The method according to claim 4, characterized in that - when the output speed (n2) or vehicle speed decreases to or below the defined target speed (n2z) or target creep - the amount of the clutch torque (trq) is increased, preferably by means of Regulator the output speed (n2) or the vehicle speed to the target speed (n2z) or target creeping speed is adjusted. For this 1 sheet drawings