FR2825435A1 - Control of descent of a slope for vehicle fitted with an automatic clutch, uses gearbox rotational speed to trigger engagement and disengagement of the clutch and controls clutch to allow some slippage - Google Patents

Abstract

The control procedure is activated when the vehicle descends a slope. The clutch disengages when the rotational speed of the gearbox falls below a set speed and re-engages when the gearbox speed rises above a set speed. The engagement and disengagement of the clutch is regulated to ensure smooth descent, with slippage of the clutch adjusted to maintain smooth operation.

Description

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Control method for descending a slope of a vehicle with an automatic clutch
The invention relates to a control method for the descent of a slope by an automatically operated clutch vehicle, in which this operating situation is detected and, when descending a slope, the clutch mechanism is opens automatically when the gearbox rotation speed exceeds, by lower value, a first value to be prescribed and the clutch mechanism closes again when the gearbox rotation speed exceeds, by higher value, a second value to be prescribed.

 In the case of vehicles with automatic clutch, in the case of the descent of a slope, that is to say, within the meaning of the invention, a descent with little or light or no operation of the accelerator pedal and / or the brake pedal, a cyclic opening and closing of the clutch mechanism can occur at low speed. This leads to a vibration of the vehicle which is uncomfortable for the driver. This vibration comes from the fact that, during a slow descent of a slope, the vehicle is decelerated by the drag torque of the engine (engine brake). To prevent, at too low speed, depending on the gear ratio engaged, that the engine stalls, the clutch opens if one exceeds, by a lower value, a speed of rotation of the prescribed gearbox, called threshold clutch release. With the clutch open, in the case of a descent from a slope, the vehicle accelerates again until the re-engagement threshold is exceeded by a higher value, whereupon the clutch closes. This re-engagement is done to restore the flow of force and is generally desired by the driver. The vehicle then decelerates again with the trailing torque of the engine until the declutching threshold is exceeded by a lower value and the clutch opens. This cyclical behavior leads to a vibration of the vehicle or to a chatter of the vehicle, which, in the case of vehicles with high drag torque, in particular in the case of vehicles with diesel engine, is very marked.

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 and embarrassing. Due to the repeated opening and closing of the clutch, a relatively long walking situation is established which is uncomfortable for the driver and which cannot be controlled.

 The invention therefore aims to provide a control method in which the declutching and re-clutching when going down a slope are detected and that on the clutch a vibration of the vehicle is avoided or at least reduced by means of regulation by means of targeted slip or by means of targeted modulation of the torque transmitted by the clutch.

 According to the invention, in the case of the method mentioned at the beginning, this object is achieved by the fact that the clutch mechanism opens or closes at a speed whose absolute value is less than a value to be prescribed. Preferably the opening or closing of the clutch extends over a period of time of at least three seconds, preferably at least ten seconds.

 The method according to the invention is usually converted into control software which in turn is implemented in a programmable electronic control device.

 As soon as the operating condition of the descent of a slope is recognized, the clutch mechanism opens slowly and remains open until the driver applies the brake or the accelerator pedal. It can happen that, if the clutch mechanism remains open, the vehicle accelerates slowly by itself due to the descent. From a determined speed limit, which can be significantly higher than the declutching threshold, the clutch can again close slowly. Therefore, depending on the circumstances, there may still appear a cyclic vibration which, however, due to the slow closing of the clutch mechanism, the frequency is significantly lower than that corresponding to the grazing of the vehicle and therefore does not stand out much . In a particular embodiment, the vibration of the vehicle is greatly reduced by a very slow closing and opening of the clutch mechanism. For example if, when going down a slope, there is a very slow declutching,

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 for example over at least 3 seconds or in particular over at least 10 seconds, and if, simultaneously, the clutch release speed is prescribed very low, then the clutch mechanism opens substantially later than in the case of the process known and the vehicle is accelerated again later by the effect of the descent of a slope, clutch mechanism open. Therefore the frequency of the vibration is very greatly reduced. The amplitude of the vibration can also be reduced by lowering the declutching threshold with simultaneously a small hysteresis for re-engagement, so that the vibration is barely perceptible to the driver.

 In another mode of the method, after the detection of the running situation of the descent of a slope, the clutch mechanism is kept completely or partially closed. With regard to the partially closed clutch, this is obtained for example by applying a torque transmitted by the clutch which is slightly greater than the drag torque of the engine. This can also be obtained by applying a constant torque, for example as a function of the gear ratio engaged. As a result, the engine continues to slow down regularly. When the idle speed is reached, it can be maintained by means of an idle regulator. This prevents the engine from stalling. Vehicle vibration can thus be largely eliminated. In addition, the clutch mechanism can open shortly before the idle speed is reached and remain open until the driver operates the brake or the accelerator pedal.

 In the context of the desired objective, a variant of the control method is characterized in that the clutch remains only sufficiently open so that a torque to be prescribed is transmitted from the gearbox to the engine by the clutch mechanism.

 Other solutions for this purpose consist in the method mentioned at the beginning, for which the acceleration or the speed of the vehicle or the slip of the clutch is regulated. Within the meaning of this invention, this means that the clutch does not open, remains open or closes only enough so that the speed or

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 the acceleration or slippage of the clutch takes on a value to be prescribed.

 In the case of a solution by regulating the acceleration of the vehicle, if the descent of a slope is recognized, there is switching to a regulation of the acceleration of the vehicle. The acceleration is either measured or determined by derivation from the speed of rotation of the gearbox (optionally also the speed of rotation of the speedometer hose or the speed of the wheels). Following the prescription of a prescribed acceleration, the actual acceleration approaches the prescribed acceleration and the torque transmitted by the clutch changes so that a variable slip speed occurs which ultimately regulates the acceleration. of the vehicle.

 In the case of the solution by regulating the speed of the vehicle, if the descent of a slope is recognized, there is switching to a regulation of the speed of the vehicle. The speed is either measured or determined from the speed of the gearbox (optionally also the speed of the speedometer hose or the speed of the wheels). As a result of the prescription of a prescribed speed, the actual speed approaches the prescribed speed and the torque transmitted by the clutch changes so that a variable slip rotation speed occurs which ultimately regulates the speed of the vehicle.

 In the case of the solution by regulating the speed of rotation of the slip, if the descent of a slope is recognized, there is switching to a regulation by the speed of rotation of the slip. As a result of the prescription of a prescribed slip speed, the actual slip speed approaches the prescribed slip speed and the torque transmitted by the clutch changes so that a speed occurs. constant sliding rotation.

 The invention is explained in detail below using the drawings.

 Figure 1 shows the schematic appearance of the speed of

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rotation at the input of the gearbox nbdv, the speed of rotation of the engine nmot and the torque transmitted by the clutch ME, each time as a function of time t during the descent of a slope, in the state of technique and
Fig. 2 shows the schematic shape of the speed of rotation at the input of the gearbox nbdv, of the speed of rotation of the motor nmot and of the regulation, by the slip in accordance with the invention, of the torque transmitted by the clutch ME, each time as a function of time t during the descent of a slope, the presentation being for example for the regulation of the rotation speed by sliding.

 At the beginning of the descent of a slope of a vehicle with an automated clutch mechanism, neither the brake nor the accelerator pedal being actuated, according to FIG. 1 the speed of rotation at the entrance of the gearbox nbdv speeds and the engine rotation speed nmot, with the clutch closed, are first of all of the same value and decrease over time. The torque transmitted by the ME clutch is constant.

As soon as the speed of rotation at the input of the gearbox nbdv exceeds, by a lower value, a speed of disengagement of the clutch prescribed at time tA, the clutch mechanism opens under the action of the control of the known clutch, to prevent the engine from stalling. The fact that it is possible to exceed, by a lower value, the clutch rotation speed comes for example from the drag torque which, the clutch being closed, is transmitted and slows down the vehicle on the descent of a slope. If, after opening the clutch, there is no intervention by the driver by applying the brake, the vehicle accelerates (freewheeling) due to the slope of the roadway and the speed of rotation at the entrance of the nbdv gearbox increases while the engine rotation speed nmot remains constant and the torque transmitted by the ME clutch is zero (clutch open). As soon as at instant tE the speed of rotation at the input of the gearbox nbdv exceeds, by higher value, a prescribed speed of re-clutching, the clutch mechanism closes and the torque transmitted by the clutch ME increases, as does the engine rotation speed nmot. Speed

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 engine rotation speed nmot becomes equal to the speed of rotation at the input of the gearbox nbdv until reaching an intermediate maximum. If one continues not to apply the brake, as a result of the control of the automated clutch mechanism, the speed of rotation at the input of the gearbox nbdv decreases, the torque transmitted by the clutch ME decreases, as well as the engine speed nmot and, when the speed at the input of the gearbox nbdv drops below the clutch speed, the clutch mechanism opens and the process already described is repeated. In the extreme case this process is repeated cyclically and causes an undesirable chatter of the vehicle or vibrations of the vehicle which are perceived by the driver as unpleasant and dangerous.

 These cyclic vibration processes should be avoided or minimized by the invention. For this purpose we explain with the help of Figure 2 how the situation of the descent of a slope, which triggers a declutching and a re-clutch, is recognized and whose clutch control is triggered by a regulation by slip (or one of the other methods described), by means of which the appearance of vibrations is suppressed by targeted modulation of the torque transmitted by the clutch. As shown in FIG. 2, the curve of the speed of rotation at the input of the gearbox nbdv t of the speed of rotation of the engine nmot as well as that of the torque transmitted by the clutch ME, up to instant tE, these curves largely correspond to the known processes in the case of the known clutch control, as shown in FIG. 1. Event a) is first detected, that is to say disengagement without brake operation at time tA, then event b), that is to say re-engagement at constant engine speed nmot. As soon as event a) is recognized, an engine-brake-vehicle marker is validated in the control program. If event b) is recognized, the two conditions, the engine-brake-vehicle marker and event b) lead to the fact that a re-clutch marker for the descent of a slope is validated.

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 In the case of regulation by sliding, the following action is executed: the torque transmitted by the clutch ME (initially zero) increases under the action of the control, for example the growth takes place in the form of a ramp or scale interval, until the speed of rotation at the input of the gearbox nbdv is less than / equal to a range of the speed of rotation formed by the speed of the motor nmot plus a constant regulation deviation (deviation) of for example 50,100, 150 rpm. The torque transmitted by the clutch ME is then modulated so that a negative sliding rotation speed ng = ot-nbdv appears at the clutch. From the two relations nbdv = nmot + deviation and ng = nmot-nbdv results the negative sliding rotation speed ng according to ng = (-) deviation. Examples for the prescribed sliding rotation speed ng are then -50 rpm, -100 rpm, -150 rpm or other multiples of a basic sliding rotation speed ng = -50 rpm, ng = -40 rpm or -60 rpm.

 During the sliding regulation, as shown in figure 2, the torque transmitted by the clutch ME is regularly modulated and one does not arrive at a disengagement, that is to say at no time the torque transmitted by the clutch is zero. It is advantageous to lower the regulated speed of the torque transmitted by the clutch in order to avoid excessive modulation of the torque transmitted by the clutch and to largely avoid vibrations of the vehicle. Due to the slip regulation, the vehicle then runs, engine at idle, at a largely constant speed down the slope and there is largely no cyclic opening and closing of the clutch mechanism.

 As an entry condition for re-engagement in the descent of a slope according to the invention, a limit value is also provided for the temperature of the clutch mechanism which must not be exceeded by any higher value. This limit value is for example 300 C. For this purpose, a detector continuously measures the temperature of the clutch mechanism or else the clutch control calculates it by means of a calculation process, a temperature which increases all the more strongly that the couple

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 dragging of the transmitted engine is more important.

 The end of the targeted clutch modulation to combat vehicle vibrations when going down a slope occurs in the presence of exit conditions which are described below.

In one embodiment, the control method, in accordance with the invention, for modulating the targeted clutch to combat the vibrations of the vehicle when going down a slope takes the following embodiment:
In the case of the control process, two successive events are first of all monitored by the control software: a) declutching without applying the brake; b) re-engagement after declutching without increasing the engine speed. This corresponds to the driving behavior desired by the driver. The declutching can be recognized when the rotation speed at the input of the gearbox nbdv is lower than the declutching threshold and that the change in time dnbdv / dt (gradient of nbdv). is less than 0 or a negative threshold value (corresponds to decreasing nbdv) and that a brake (walking brake and / or parking brake) is not, or only slightly, operated. In addition, the last two conditions can be observed over a certain rotation speed interval: declutching is recognized if nbdv decreases, with a speed composed of the declutching threshold (ndebr) and a deviation (for example 50 tmp) up to the declutching threshold without a brake being (strongly) operated. After the clutch is detected, an engine-brake-vehicle marker is validated which is invalidated as soon as the driver intervenes by (fairly strong) operation of the accelerator pedal and / or the brake.

When the declutching threshold is exceeded, by a lower value, the clutch mechanism opens according to a standard strategy. The re-engagement is defined by the override, by a higher value, of the disengagement threshold by the speed of rotation at the input of the gearbox nbdv, the engine-brake-vehicle marker being still validated.

 In another embodiment, the following aspect is also favored:

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Neither the brake nor the accelerator pedal being operated, the descent of a slope is, among other things, detected as follows: when, when going down a slope, the clutch mechanism opens shortly before that the clutch mechanism is fully open, the engine speed changes relative to the gearbox speed. The speed of rotation of the gearbox is then greater there than the speed of rotation of the engine because, when going downhill, with the clutch mechanism open or partially open, the vehicle accelerates. However, the speed of rotation of the gearbox can therefore also become greater than the speed of rotation of the motor because it decreases more slowly than the speed of rotation of the motor. We then have a negative shift.

 It can also be requested that the speed of rotation of the gearbox be greater than the speed of rotation of the engine for more than a predetermined period of time (for example 300 ms).

 This can be used as a condition for the presence of the descent of a slope. On the contrary, in the plain, the speed of rotation of the engine is always higher than the speed of rotation of the gearbox because in the plain the vehicle is slower. In this case we have a positive slip.

 Another criterion for the presence of the descent of a slope is that after declutching the speed of rotation of the gearbox remains constant or increases. As a result, the speed of rotation of the gearbox or a corresponding derived quantity is detected, such as the speed of rotation of the wheels or the speed of rotation of the speedometer hose, or else use is made of the derivative, as a function of time, of these quantities (gradients of the speed of rotation of the gearbox, of the speed of rotation of the wheels or of the speed of rotation of the hose of the speedometer).

 In another embodiment, it is further requested that the torque currently transmitted by the clutch is equal to 0.

 The entry condition for re-engagement in the

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 In the case of a descent from a slope, the brake-vehicle marker is validated and the re-clutch is recognized. In addition, it is also possible to request, as another condition, that the temperature of the clutch mechanism be lower than a limit temperature of, for example, 3000 C. If these two or three conditions are fulfilled, a marker to re-engage for the descent of a slope is validated in the software.

 In addition, it can also be requested as another condition that the clutch control is not in a state which is during or shortly after a gear change.

The mode of targeted modulation of the clutch to combat the vibrations of the vehicle when going down a slope is abandoned, that is to say that the marker re-engage-for the descent of a slope is disabled in the case where one or more of the following conditions is (are) met:
The brake is operated for a time tl of for example more than Os or 1 s (with a determined force); the accelerator pedal is operated to a minimum value (threshold value) greater than for example 0, preferably for more than, for example, Os at 0.5 s; the speed of rotation at the input of the nbdv gearbox is greater than a threshold of for example 300 rpm, for safety reasons; the speed of rotation at the input of the gearbox nbdv is lower than a speed of rotation of the idle-gap (for example gap = 0 to 50 rpm), this serves as protection to prevent the engine from stalling and the temperature of the clutch mechanism is greater than a value, for example a threshold of 300 C. This is another output condition that can represent the request or the recognition of a gear change.

 When abandoning the targeted modulation mode of the clutch to combat vehicle vibrations when going down a slope, there is again a return to the previously active clutch control. This return can be done directly or after an equalization of the prescribed torques from the modulation during the descent of a slope and the command

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 the clutch used in other walking situations (for example in the form of a ramp).

 A programmable electronic control device which has inputs connected to means for detecting the speed of rotation of a motor and / or a gearbox and / or a speedometer hose and / or wheels and / or a gearbox report to be engaged and / or engaged, and which has outputs for sending control signals to an electrically operated clutch device, is characterized in that the control device is modified or programmed so that each of the previous control processes is feasible.

 With regard to the electronic control regulation devices with the appropriate detectors and operating means and with regard to the corresponding control and regulation method in vehicles with automated clutches and gearboxes, this point is expressly referred to. from view to documents DE 40 11 850 Al, DE 44 26 260 Al, DE 197 45 677 Al and EP 1 010 606 Al.

 The claims filed with the application are proposed formulations without prejudice to obtaining additional protection. The applicant reserves the right to claim yet another combination of characteristics which has so far only appeared in the description and / or in the drawings.

 References used in the subclaims draw attention to the alternative conception of the subject matter of the main claim due to the features of the respective subclaim; they should not be understood as a waiver of obtaining specific, concrete protection for the combinations of characteristics of the referenced sub-claims.

 Due to the fact that the objects of the sub-claims may, with regard to the technique at the priority date, constitute own and independent inventions, the plaintiff reserves

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 be the subject of independent claims or divisional claims. They may furthermore also contain own inventions presenting a construction independent of the subjects of the independent subclaims.

 The exemplary embodiments are not to be considered as a limitation of the invention. Rather, in the context of this presentation, many variants and modifications are possible, in particular variants, elements and combinations and / or materials which, for example by combining modifications of certain elements in connection with the characteristics or elements or not process described in the general description and in the embodiments as well as in the claims and contained in the drawing, can be concluded by a person skilled in the art having regard to the solution making it possible to reach the aim and lead, by characteristics which can be combined, to a new object or to new process steps or to new process sequences, also insofar as they relate to production, control and work processes.

Claims (11)

Claims 1. Control method for descending a slope by an automatically operated clutch vehicle, in which this operating situation is detected and, when descending a slope, the clutch mechanism opens automatically when the speed of rotation of the gearbox exceeds, by lower value, a first value to be prescribed and the clutch mechanism closes again when the speed of rotation of the gearbox exceeds, by higher value, a second value to be prescribed, characterized in that the clutch mechanism opens or closes at a speed whose absolute value is less than a value to be prescribed. 2. Control method according to claim l, characterized in that for the opening or closing of the clutch mechanism is provided a period of time of for example at least three seconds, in particular at least ten seconds. 3. Control method for descending a slope by a vehicle with an automatic clutch, in which this operating situation is detected and, when descending a slope, the clutch mechanism opens automatically when the speed of rotation of the gearbox exceeds, by lower value, a first value to be prescribed and the clutch mechanism closes again when the speed of rotation of the gearbox exceeds, by higher value, a second value to prescribe, characterized in that the clutch mechanism remains only sufficiently open for a torque transmitted by the clutch to be prescribed to be transmitted from the gearbox to the engine. 4. Control method according to claim 3, characterized in that the torque transmitted by the clutch to be prescribed corresponds substantially to 0 Nm. 5. Control method according to claim 3, characterized by <Desc / Clms Page number 14>  the fact that the torque transmitted by the clutch to be prescribed depends on the gear ratio engaged.  6. A control method according to claim 3,4 or 5 characterized in that the torque transmitted by the clutch to be prescribed is chosen a little greater than the drag torque of the engine.  7. Control method according to one of claims 3 to 6, characterized in that the clutch mechanism opens completely when the engine speed corresponds to the idle speed.  8. Control method for descending a slope by a clutch vehicle with automatic actuation, in which this operating situation is detected and, when descending a slope, the clutch mechanism opens automatically when the speed of rotation of the gearbox exceeds, by lower value, a first value to be prescribed and the clutch mechanism closes again when the speed of rotation of the gearbox exceeds, by higher value, a second value to Prescribe, characterized in that the clutch mechanism only opens sufficiently for the vehicle to accelerate to a value to be prescribed.  9. Control method according to claim 8, characterized in that the acceleration is measured as a function of the change, over time, of the speed or of the speed of rotation of the gearbox, of the speed of rotation wheels or the speed of rotation of the speedometer hose.  10. Control method for descending a slope by a clutch vehicle with automatic actuation, in which this operating situation is detected and, when descending a slope, the clutch mechanism opens automatically when the gearbox speed exceeds, by a lower value, a first value to be prescribed and the clutch mechanism closes again <Desc / Clms Page number 15>  when the speed of rotation of the gearbox exceeds, by a higher value, a second value to be prescribed, characterized in that the clutch mechanism only opens sufficiently so that the vehicle speed corresponds to a value to be prescribed . He. Control method according to claim 10, characterized in that the speed is measured as a function of the speed of rotation of the gearbox or that it is determined from the speed of rotation of the wheels or the speed of rotation of the speedometer hose.  12. Control method for descending a slope by a clutch vehicle with automatic actuation, in which this operating situation is detected and, when descending a slope, the clutch mechanism opens automatically when the speed of rotation of the gearbox exceeds, by lower value, a first value to be prescribed and the clutch mechanism closes again when the speed of rotation of the gearbox exceeds, by higher value, a second value to prescribe, characterized in that the clutch mechanism only opens sufficiently so that the difference between the speed of rotation of the gearbox and the speed of rotation of the engine corresponds to a value to be prescribed (regulation by sliding ). 13. Control method according to claim 12, characterized in that the value to be prescribed in the case of regulation by sliding is chosen over a range of -40 to -100 rpm.  14. A control method according to claim 12 or 13, characterized in that the regulation is ended by sliding if the operation of a brake or the accelerator pedal is detected, if the speed of rotation of the gearbox is greater than a safety threshold value to be prescribed, if the engine speed is lower than the idle speed or if the temperature of <Desc / Clms Page number 16>  the clutch is higher than a threshold temperature to be prescribed. 15. Control method according to one or more of claims 1 to 14, characterized in that the speed of rotation of the engine, the speed of rotation of the gearbox, the operation of the accelerator pedal and of the brake are monitored continuously and that a descent from a slope is determined by the fact that, the clutch mechanism being disengaged, the accelerator pedal not being or only slightly or little actuated and the brake being not or only little or slightly operated, the speed of rotation of the gearbox is greater than the speed of rotation of the engine. 16. Control method according to claim 14, characterized in that another condition for the presence of the descent of a slope is that after declutching the speed of rotation of the gearbox remains constant or increases .  17. Control method according to claim 14 or 15, characterized in that instead of or in addition to the speed of rotation of the gearbox, the speed of rotation of the wheels, the speed of the vehicle or the speed of Rotation of the speedometer hose is detected to determine the descent of a slope.